Crystal Instruments SPIDER20 MINI-DYNAMIC SIGNAL ANALYZER AND DATA RECORDER User Manual Spider 20 20E Manual

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Figure 180:3D Color map of an FFT spectrum
With a 3D RPM frequency spectrum, the variation of components of frequency with
respect to the RPM can be clearly observed. A clear differentiation of the spectral
components that depend on the rotational speed (forcing orders) and the spectral
components that do not (resonances) is clearly shown.
Band RMS Spectrum
In order tracking, it is also important to monitor the overall RMS level or signal
power level of the measurement versus RPM. The overall level is a good tool to
rapidly identify critical bands of operating RPM. Overall level can be in unit of RMS
(EUrms) or power (EUrms2). The horizontal axis is RPM. Below is a typical overall
level display.
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Figure 181: Overall RMS level plot
A list of common sources of vibration in a rotating machine includes:
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Order
0.05X~0.35X
0.43X~0.49X
0.5X
0.65X~0.95X
1X
1X+2X
(#Vane)X
(#Blades)X
Source of Problem
Diffuser Stall
Instability
Rubbing
Impeller Stall
Imbalance
Misalignment
Vane/Volute gap
Blade/Diffuser Gap
Raw Data Time Streams
In many competitive tracking software products, the user can either conduct realtime order tracking, or record the data with other tools and then post-process the
order tracks, but not both. The Spider, in conjunction with the Crystal Instruments
EDM software can perform real-time order analysis and tracking and
simultaneously record the time streams of all channels including the dedicated
tachometer channels. Crystal Instruments Order Tracking can record up to 128
signal channels and two tachometer channels while performing real-time order
tracking and analysis.
Crystal Instruments Post Analyzer software can use the recorded signals to perform
off-line Order tracking and Analysis. Real time processing limitations, if they exist,
can be overcome using this feature.
Phase for Order Tracks
The Phase in Rotating Machine Analysis
Many mechanical faults are associated with certain orders, analyzing both
ordermagnitude and its phase can help you detect mechanical faults directly.
Forexample, a strong first order magnitude indicates imbalance in most
cases.Analyzing the first order magnitude can help you identify an imbalance
problem.Moreover, the magnitude and phase of the first order can help you correct
the problem by adding weights on the appropriate rotor positions. While it is
possible to balance a machine using magnitude-only measurements, employing
measured magnitude and phase reduces the number of machine stop/starts in the
balancing process by a factor of three or more.
As previously discussed, an order track is the measurement taken for an order, i.e.,
normalized frequency, versus RPM. In most of the applications of engine related
test, the phase information of order tracks are not important. In rotating machine
analysis, the phase of the signal is vitally important.
Phase is a relative quantity and can only be measured between a pair of signals. It
indicates the time delay (at certain frequency) between the two signals. The phase
value can be translated into the difference in relative angle, relative position or
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propagation time if additional information is known. (When we refer to the singlechannel phase, we speak of its phase is relative to the start point of its data block.)
In rotating machine analysis, the phase of the first order of a rotor can be directly
mapped to an angular difference between a signal and a reference. The reference
signal can be another channel of measurement, or the tachometer signal. The phase
difference between two waveforms is often called a phase shift or phase delay.
Phase shift may be considered positive or negative, i.e., one waveform may be
delayed relative to another one, or may precede it in time. These conditions are
called phase lag and phase lead respectively.
An example of this is the phase of an imbalance component in a rotor with
reference to a fixed point on the rotating rotor, such as a shaft keyway. To measure
this phase, a trigger-pulse must be generated whenever the keyway passes a fixed
point. An optical, magnetic or eddy-current probe may be used to generate such a
―tach‖ pulse signal.
Heavy
Spot
Phase
Angle
Reference
Position
A zero degree phase delay at a frequency can be depicted as a series of pulses
overlaid with a sine wave where the pulse edge is exactly located in peak position of
the sine wave.
Reference
Pulses
Zero
degree
phase
In the figure above, a section of the tachometer signal is shown on its own and then
overlaid on the vibration signal. The tachometer signal in this example crosses the
vibration signal at exactly the same point on each cycle. If the phase of the vibration
signal were to change (as it would with a slight speed change), then its position
relative to the tachometer pulse would also change. Extracting the first order
magnitude and phase, gives the curves shown below. The phase is now constant
near -60o as it should be for such a signal. Because the rotating period of the signal
is about 20 ms, -60o corresponds to a 20*60/360=3.3 ms delay.
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Phase measurement at higher orders will exhibit similar behavior, although they
are more difficult to comprehend intuitively.
It must be noted that Complex Order Tracks order tracks with phase, are not
regular complex signals as frequency response or cross spectrum. They are really
auto spectra with assigned phase. These synthesized signals can certainly be viewed
as a complex signal using tools including Bode Plot, polar and orbit diagram.
However the user must keep in mind that the magnitude and phase of a complex
order track are calculated separately.
Bode Plot
The term Bode Plot is borrowed from the field of control theory, referring to a plot
of magnitude and phase angle between the input and output verses frequency of a
control system. Many in the rotating machine vibration industry have adopted this
term to describe the steady-state vibration response amplitude and phase angle
versus rotational speed (RPM). It turns out that the Bode Plot is the best way to
describe order tracks with phase. You typically use Bode plots for transient
analysis in both Run-up and coast-down conditions. A Bode plot can help to
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identify the resonance speed of a rotor or examine the rotor dynamics on an
order basis.
In the Spider 80X system, after the order tracks with phase are acquired, the Bode
Plot can show one or multiple tracks. Spider 80x system is also capable of
calculating phase plots to specifically measure the Run-up and Coast-down
conditions. A typical bode plot is shown below:
Figure 183: Typical Bode Plot
Operating Spider system
Crystal Instruments developed an enhanced Spider system with dedicated
tachometer channels and an enhanced hardware circuitry for measuring the
tachometer signal and performing order analysis. All Spider devices with hardware
versions 7.5 and above possess these special capabilities. It allows them to perform
Order Spectra, Order Tracks, FFT Spectra and Band RMS Spectra simultaneously.
Older Spider modules (7.4 and back) developed without the dedicated tachometer
channels can also be used to perform order tracking. One or two of the input
channels can be used as tachometer channels and one of them can be used as a
Reference tachometer channel to perform the order analysis functions.
This section focuses on using the EDM to create a test for performing Order
Analysis and tracking. Based on the previous discussion, 3 measurements are of
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prime significance in Order tracking. Order Spectrum and Order tracks with phase,
Continuous frequency spectrum or the FFT Spectrum and the Band RMS Spectrum.
In this section, a detailed description on creating and measuring each of the
measurements is given starting with creating and setting up the basic properties of
an Order Tracking test. The following description is valid for both dedicated
tachometer compatible hardware units (7.5 and above) and non-compatible units
(7.4 and below) unless and otherwise specified. Henceforth, we designate the
dedicated tachometer compatible units as ―7.5 Hardware‖ and the non-compatible
units as ―7.4 Hardware‖
Creating a Test
Order tracking is found under the ―Dynamic Signal Analysis‖ section of the EDM.
Click on the Dynamic Signal Analysis to see the option for Order Tracking.
Figure 184: New Test Wizard
Click on Order tracking to begin the process of creating a new test in Order
Tracking and click on ―Next‖, as shown below.
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Figure 185: New Test Wizard – Order Tracking
Enter a valid test name in the Test Name field and an optional description of the
test can be added in the Test Description field. Select an appropriate Spider System
and test directory and click on ―Next‖ to continue.
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Figure 186: New Test Wizard – Selecting Tachometer channels (7.5
Hardware and above)
In 7.5 hardware unit(s), tachometer/output channels can be selected as the
dedicated tachometer channels. The user can turn Tachometer Channel 2 ON or
Turn OFF, depending on the specific user requirement. The Reference tachometer
is always Output Channel 1 or Tachometer Channel 1. Tachometer Channel 2
(Output Channel 2) can only be used to calculate RPM and does not support Order
analysis functions in any other way.
In the 7.4 hardware unit(s), output channels are not capable of performing the
tachometer measurements, so one or two of the input channels must be designated
as a tachometer channels. The choice of selection of the tachometer channels can be
made by the user. Any input channel of the master module (only) may be used.
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Figure 187: New Test Wizard – Selecting Tachometer channels (7.4
Hardware and below)
User must have at least one tachometer channel enabled to perform the order
tracking functions. Use of the second tachometer is optional.
One of the tachometer channels (when tachometers are selected) must be used as a
reference tachometer in order to perform the order analysis. User has the choice to
select one of the two tachometers as the Reference Tachometer.
Click on ―Finish‖ to create the test.
Once the test is created, a blank test with no signals can be viewed. The following
Figure shows the basic User Interface when the test is created.
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Figure 188: Order Tracking Test – Initial EDM Screen
The Test screen is divided into 5 parts. On the left side, there are the Recent Test
List and the Signal List. On the right there are the Control Panel and the Status
Window. In the middle are the Signal Display and Signal Setup tabs.
Recent Test List
Figure 189: Recent Tests
On the upper left part of the screen, the Recent Tests list shows current and
previous tests. Each test is listed by its name and type (VCS or DSA). Each test entry
is expandable to display items underneath related to the test.
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System lists the hardware modules associated with this test. The system is
set up using the Spider Config window, described under System
Configuration. The name of the system is displayed in parentheses.
Signal List
Under the Recent Tests list is the Signal List, which shows live signals and saved
data available for display.
Figure 190: Live Signals
Live Signals include all input channels that are a part of the current system.
(Depending on the test type, there may be other signals such as the control profile,
associated alarm, and abort lines.) The list is divided in categories for time streams,
RPM Signals and Order Tracking Spectra. It can also be viewed according to the
hardware modules by right-clicking on the list and selecting Sort Signals by Spider
Modules.
Run Folders tab displays the recent Runs:
After the user presses the Run button and the test finishes, a ―run‖ is generated. By
default, a Run folder is created on the disk.
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Figure 191: Run Folders
Data Files are time streams and block data saved or recorded to disk. All of the data
files under a specific Run will be saved into that Run folder. When block signals are
saved by clicking the Save Sigs button, a data file will be created and displayed
here.
Figure 192: Data Files
Control Panel
The Control Panel is used to control the test and display status information in realtime. The connection status of the hardware is shown on top, with a button to
Connect/Disconnect (if no hardware is detected, this button will not be displayed).
The control buttons — Run, Hold, Stop,Save— duplicate the items in the Control
menu and on the Control toolbar. Config opens the Test Configuration window.
Rec./Stop starts/stops the recording after test runs.
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Below the control buttons, information on the state of the test is displayed. For a
typical Order tracking test, the total elapsed time and the RPM of the enabled
tachometer channels is displayed.
A few key parameters that are important to the Order Analysis are also displayed.
These settings can be changed from the Test Configuration Setup which will be
dealt with later in this section.
The function buttons are used to undertake specific functionalities.
Turn Output On / Off: Output channels can be used as output when 7.4
hardware units are used or when a tachometer is disabled in a 7.5 hardware unit.
This button turns an available output channel(s) On or Off.
Limit Check On / Off: Turns ON or OFF the limit checking capability of the test.
Limits can be enabled on all the order analysis signals to trigger a user defined
event when the signal crosses a limit. The limits can be defined individually for each
signal. Limit functionality will be revisited later in this section. This button
determines when the limit checking is enabled.
Setup Tachometer navigates to the ―Tachometer‖ section of Test Configuration
page where the parameters for the tachometer channel(s) can be set.
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There are tabs on the bottom of the control panel for viewing different pages of
information. The Cursor tab shows the abscissa and ordinate values for all
displayed cursors and peak and harmonic markers.
There are Input, Output, and Cursor tabs. The Input tab is shown above. The
Output tab controls the output function generator. Cursor shows the details of the
cursor when a cursor is placed on displayed signal.
On the very bottom of the control panel the system connection status is shown,
along with any messages related to test events.
Tachometer Setup
Spider-80X units are capable of handling two tachometer channels. The 7.5
hardware units have dedicated tachometer 1 to perform Order Analysis and
tracking as well RPM measurement and recording. Tachometer channel 2 only
performs RPM measurement and recording. The 7.4 hardware units can have any
of the input channels up to two can be used as the tachometer channel(s) with one
of those channels being used to perform the order analysis.
In 7.4 hardware units, only 1 0r 2 input channels from the master module can be
used as a tachometer channels. In version 7.5 hardware units, only the tachometer
channels from the master module can be used as tachometer channels.
Tachometer parameters need to be set for the tachometer to detect the tachometer
pulses correctly and generate an accurate RPM signal.
To setup or modify the tachometer settings, click on ―Config‖ from the Control
Panel and select ―Analysis Parameters‖ on the left or click on ―Setup Tachometer‖
from the control panel function buttons. They both open the same page which is
shown below:
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Figure 193: Test Configuration for Order Tracking
The Right side of this page deals with the tachometer settings.
Reference Tachometer Channel: Identifies the Reference Tachometer channel
that is used for calculating the Order spectrum, Order Tracking. This setting is only
useful when using a 7.4 hardware units in which one of the two tachometer
channels can be used as a reference tachometer channel. In the 7.5 hardware units,
the Tachometer channel 1 / Output channel 1, is always used as the Reference
Tachometer.
The typical settings of the tachometer are listed below:
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Tachometer Channel identifies the channel used as Tacho 1 (or 2). The
checkbox can be used to enable or disable the tachometer channel and the
dropdown menu lists all the channels that can be used as a tachometer channel.
For the 7.4 hardware units, any input channel from the master module can be used
as a tachometer channel. For the 7.5 hardware units, the dedicated tachometer 1
channel is used as the Tachometer channel 1 and is enabled at all times. The
dedicated tachometer channel 2 is used as tachometer channel 2 and the user has
an option to enable it or disable it.
Pulse Edge Type specifies triggering upon the rising or falling edge of the
tachometer pulse.
Pulse per Revolutionis assumed from each revolution. The tachometer may
generate one or multiple pulses per revolution of the rotating machine. The number
of tachometer pulses that need to be counted to complete one machine revolution is
set using this parameter. The minimum value of this parameter has to be 1.
Pulse Edge Value is the threshold voltage level that the input tachometer pulse
needs to exceed to be detected as a pulse.
Acquisition Mode controls the processing of the tachometer signal.
Free Run – data is acquired regardless of the direction of the RPM as long as
the RPM is between the low and high RPM limits.
Run Up – data is only acquired when RPM starts below low RPM limit and
then increases. Acquisition stops when RPM exceeds high RPM limit.
Run Down – data is only acquired when RPM starts above high RPM limit
and then decreases. Acquisition stops when RPM exceeds low RPM limit.
Up Down – data is only acquired when RPM starts below low RPM limit
and increasing. Acquisition continues as RPM increases past high RPM
limit and then as RPM decreases past the low RPM limit.
Down Up – data is only acquired when RPM starts above high RPM limit
and decreasing. Acquisition continues as RPM decreases past low RPM
limit and then as RPM increases past the high RPM limit.
Pulse Detection Resolution is a hysteresis value applied to the trigger transition
voltage. If a rising edge is specified, a low state must be at least the pulse detection
resolution below the pulse edge value. If a falling edge trigger is specified, this
constraint applies to the pre-trigger high state.
The same settings are also applicable for the Tachometer 2, if enabled.
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Order Analysis Parameters Setup
To setup the Order Analysis parameters, click on the ―Config‖ button on the Control
panel or navigate to ―Test Configuration‖ from the ―Setup‖ menu item. This will
open the same page which is used for the tachometer setup.
The left side consists of two important sections for settings, the upper one is the
Order Analysis parameters setup and the lower one is the FFT Analysis parameters
setup.
In this section, we will discuss the Order Analysis parameters setup. These
parameters are used for calculating the Order Spectrum, Order Tracks and Band
RMS Spectrum.
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Figure 194: Order analysis parameters
Low/High RPM:The Low and High RPM define the range of RPM for RPM
measurements, Calculation of Order tracks and Band RMS Spectra. If the Spider80X detects that the current RPM is between the Low and High RPM, it will take
the measurement and display it. Otherwise, the RPM readings on the control panel
will always display 0 and the RPM time streams will always display the value of Low
RPM.
Delta RPM: The Delta RPM defines the resolution of the RPM trace or the
resolution of the RPM axis for Order tracks and Band RMS Spectra. The smaller the
delta RPM, the more frequently the signals will be stored and displayed along the
RPM axis and the more storage that will be required. Typically the Delta RPM is
chosen between 25 and 100 RPM.
Max Order: The Max Order defines the highest order number for an Order
Spectrum. This is similar to defining the maximum frequency in an FFT analysis.
EDM uses this value to determine the analysis frequency range. You should define
the minimum Max Order that the application needs. If the Max Order too high, the
system must sample at a very high frequency to cover the whole frequency range
and the accuracy of lower order estimations may be poor.
Delta Order: The delta Order defines the resolution of an Order Spectrum. The
Max Order and Delta Order together define the number of points in a normalized
order spectrum. The smaller the value of Delta Order, the better will be the
resolution and more computational resources are required to process the order
spectra.
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The Order Analysis parameters can also be viewed or edited on the control panel
(when the test is not in the running). This enabled the users to quickly access and
modify the Order Analysis parameters which are the most important parameters
for an Order Tracking test.
FFT Analysis Parameters Setup
As mentioned in the previous section, it is frequently important to measure the FFT
Spectrum alongside the Order spectrum during an Order Analysis. FFT parameters
can be modified by navigating to the Test Configuration, by either clicking on
―Config‖ from control panel or clicking on ―Test Configuration‖ from the ―Setup‖
menu item.
The frequency range and other FFT parameters are usually determined using the
max order and the max RPM of the order analysis settings. Some key parameters
can be changed by the user to enable the FFT spectrum as per the user‘s choice.
Frequency Range is defined as the maximum frequency range for the FFT
analysis. Frequency range determines the sampling rate required. A minimum
frequency range is set depending on the maximum order and the maximum RPM
of the Order analysis. The user will be able to set the Frequency range higher than
this range to obtain a higher frequency range for FFT analysis. The user cannot
decrease the Frequency range below the minimum value set by the EDM using the
Order analysis parameters.
Overlap Ratio is the ratio of the overlap between two consecutive frames of data.
A 50% overlap signifies a 50% data in a frame is filled by the existing data and the
remaining part of the frame is filled by the new data.
Window Type defines the data windowing function used in the FFT and order
analysis.
Average Strategy – defines the averaging type used in the FFT and order analysis:
exponential, linear or peak hold.
Average Number – defines the number of averages in a linear average or the
weighting factor for exponential averaging.
FFT Average On/Off turns the averaging defined by the above two parameters
On or Off. When the Averaging is On, averaging is done on the data and when Off,
averaging is not performed.
Input Channels Setup
The Input channel setting for an Order tracking test is same as the general setting
for any other test, Refer to Input Channels Setup for the complete setup details.
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Output Channels Setup
The Output channels for the 7.5 hardware units of Spider 80X hardware are also
designed to act as tachometer channels.
The Output channel 1 is a dedicated tachometer channel which can support Order
analysis functions and must be used as a tachometer.
The Output Channel 2 can either be used as a Tachometer to calculate the RPM or
use it as an output channel to generate the desired output. Click on ―Setup‖ menu
item and select the Output Channels to view the Output Channel settings.
Figure 195: Output channels setup
Output 2, as described can be toggled between the Output Ch2 or Tach Ch2. Select
Output Ch2 when it is supposed to be used as an Output Channel.
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Figure 196: Output channel configuration in Order Tracking
The Output channel can also be enabled by simply disabling the tachometer 2 from
the tachometer settings in the Test Configuration.
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As mentioned earlier, unchecking the box next to Tachometer Channel 2 disables
the channel 2 as a tachometer input and channel 2 is set to Output.
For the 7.4, hardware units, the output channels can only be used for generating
outputs and the output channel settings can be viewed or set using the control panel
output tab or the navigating to the Output Channels setup from ―Setup‖ menu item
and clicking on ―Output Channels‖.
A more detailed description of the specific usage of the output channels to generate
different types of signals as output is described in the Output Channels section of
this manual.
Measured Signals Setup
Signals that need to be measured including the option to include selected signals in
the Record or Save list is done using the Measured Signal setup. Additionally, Order
spectrum, configuring Order tracks and RMS Band spectra can also be done using
the measured signals setup.
To open the measured signals setup page, Click on the menu item, ―Setup‖ and click
on ―Measured Signals‖.
The following figure shows the Measured Signals setup page for a typical Order
tracking test with one Spider module.
Figure 198: Measured signals setup
The signals are categorized into multiple tabs each signifying a particular class of
signals.
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Time Streams deals with the raw time stream data from the input channels. For
the 7.5 hardware units, there will be up to two tachometer channels in addition to
the input channels.
RPM Streams measure the instantaneous RPM of the tachometer channels and
displays continuously with respect to time similar to a time stream
Order Spectra measure the Order spectrum of each of the channels with the
selected reference tachometer channel for the 7.4 hardware units or with the
dedicated tachometer 1 as reference channel for the 7.5 hardware units.
FFT Spectra defines the spectrum of the channels with respect to the frequency as
the X axis. This is identical to the conventional FFT spectrum on an FFT test.
Order Tracks can configure and measure order tracked signals for a particular
channel and a particular order. One input channel can generate multiple order
tracked signals, each for a different order.
Band RMS Spectra plots the RMS amplitude in a user defined band of
frequencies versus the RPM.
3D Signal displays the signal plots in 3D.
All Signals gives a view of signals from all the tabs to the user.
Similar to the measured signals in any of the DSA or VCS tests on EDM, the time
stream signals can be recorded continuously and the other signals that appear as
blocks or frames of data can be saved to the PC or to the internal flash of the Spider.
Time stream Signals
The time stream signals are the raw time waveforms applied to the input channels.
They are displayed with relative time on the Y-axis.
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Figure 199: Measured signals setup – Time Stream for 7.5 hardware and
above
For the 7.5 hardware units, the output channels can also be used as the tachometer
input channels. Therefore, an additional two tachometer channels can be viewed in
addition to the input channels. All input channels and the tachometer channel 1
provide the raw time stream signals which are the same as the signals received at
the input channels. Tachometer channel 2, however, generates a reconstructed
tachometer signal with a unit pulse of 1V whenever a pulse in the tachometer is
detected. What does this mean?
For 7.4 hardware units, since an input channel must be used as the tachometer
channel, there is no individual tachometer channel listed.
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Figure 200: Measured signals setup – Time Stream for 7.4 hardware and
below
The input time stream signals can be Enabled/Disabled by checking the
checkboxes under the ―Measure‖ attribute. Disabling channels which are not
necessary can save memory and processing time.
The input time stream signal can also be recorded by checking the box under the
Record List against each signal. Multiple channels can be selected for recording
including the tachometer channels for a 7.5 hardware unit.
RPM Streams
RPM Streams provide the instantaneous RPM value calculated from tachometer
channel(s). This may be displayed as a time stream (versus the relative time on the
X axis).
The number of channel in this list depends on the number of enabled tachometer
channels. The following figure shows this tab‘s contents when both the tachometer
channels are enabled.
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Figure 201: Measured signals setup – RPM Streams
Similar to time streams, the Measure attribute for each signal can be checked /
unchecked to enable / disable measuring the RPM time stream signal.
The signal can also be recorded as a time stream to the internal flash when the
Record List attribute is selected for the signals that are required for recording.
Order Spectra
Order Spectra provide the spectra of the channels in terms of Orders. The following
picture shows the Measured Signals setup for the Order Spectra from a single
Spider-80X module. When multiple modules are used, the number of Order
Spectra is increased by 8 per module (up to a maximum of 128 channels).
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Figure 202: Measured signals setup – Order Spectra
Any channel for which the Order Spectrum is required must be enabled by checking
the corresponding Measure box for that channel.
Since the Order Spectra are block signals calculated every frame, each frame of the
order spectral signal can be saved by enabling the order spectra of a channel in the
Save list. Checking the Save List saves the signals when the User clicks on the
Save Signals button in the Control Panel, or when save signals is otherwise
executed.
FFT spectra
FFT spectrum is identical to the FFT calculation in an FFT Analysis test.
The following figure shows the FFT Spectra for a 16 channel (2 module) system.
The FFT Spectral signals can be measured on both Master and slave units.
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Figure 203: Measured signals setup – FFT Spectra
Similar to the Order spectra, the signals with checked Measure attribute are
calculated by the hardware and when enabled (checked) in the Save List can be
saved when the user clicks on Save Signals from the control panel or when save
signals are configured through the built-in function.
Order Tracks
Order Track signals are also of prime importance for an Order tracking test. Each
Order track retains the amplitude and phase of the selected and channel as RPM
changes. Each channel can have multiple orders that are tracked.
Since each Order Track signal needs to be configured by the User‘s, EDM software
does not enable any Order tracks by default. The required Order Tracks must be
added by the user. The following figure shows the default Order Tracks tab of the
Measured Signals setup page.
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Figure 204: Measured signals setup – Order Tracks initial setup
Click on the Add Signal button on the top to start configuring the required Order
Track signals.
Figure 205: Adding complex order track signals
Select the Channel for which an order needs to be measured and select an Order
Value. The Order value can also be a decimal number which tracks, for e.g., 1.5
order of channel 1. Click on Add to add the order tracked signal.
The Upper portion of this page, shows the Signal Name. The default name of each
signal has the form, OTRK_OrderValue(Channel Number).
Multiple orders for a single channel and multiple orders for multiple channels can
be added at the same time by selecting the channel, entering the order value and
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clicking on the Add button. The added signals list is shown at the left side of the
pane. Unnecessary signals can be removed using the ―Delete‖ button.
It has to be noted that the Order Value can take a maximum value as specified in
the Order Analysis settings and must be within the resolution selected in the Order
Analysis settings. For e.g. with Max Order setting of 10 and a Delta Order setting of
0.5, an order with a value more than 10 or an order value which is not a integer
multiple of 0.5 cannot be entered.
Figure 206: Adding complex order track signals
When all the required signals are added, click on ―OK‖ to create all the signals that
are configured by this pane.
This pane can be opened multiple times to add or modify the Order Tracks. Once
the signals are added, they appear in the Measured Signals setup window under the
Order Tracks tab as shown:
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Figure 207: Measured signals setup – Order tracks
As it can be seen, each order track entry creates 3 signals:
OTRK denotes the continuous Order Track of the selected order for the selected
input channel.
OTRK_Updenotes the signal that is only updated when the RPM is going up. When
the RPM is going down, this signal is unchanged.
OTRK_Down denotes the signal that is updated only when the RPM is decreasing
or going down and remains unchanged with the increasing RPM.
Order value can also be changed by clicking on the Order Value column of the
order tracked signal and entering a new value. It has to be noted that changing the
Order value for an order tracked signal will also change the order value for the
corresponding Up and Down signals.
The signals that are not necessary can be deleted using the delete column towards
the rightmost side.
Band RMS Spectra
A band RMS Spectrum measures the Overall RMS level in a frequency band
specified by the user. It is tracked with respect to the change in the RPM.
Configuring the Band RMS Spectra is similar to configuring the Order Tracks. It
requires the channel and the frequency range of the band. By default, the EDM does
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not have any signals under this tab and the signals need to be defined according to
user requirements.
The following figure shows the default Band RMS spectra.
Figure 208: Measured signals setup – Band RMS Spectra initial setup
Click on ―Add Signals‖ button to start configuring the Band RMS Spectrum signals.
Figure 209: Adding Band RMS Spectra
While adding the Band RMS signals,
Channel refers to the channel which needs to be measured.
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RMS Calculate refers to the band of frequencies over which the RMS needs to be
measured. The user can select Overall which spans all the frequencies governed by
the frequency range of the test.
Start and Stop Frequencies denote the start and stop frequencies of the band.
Click on Add to add the signals, the added signals can be viewed (and deleted) from
the left side section of the window.
Figure 210: Adding Band RMS Spectra
Multiple bands for the same channel can be added as shown in the Figure above.
When all the required Band RMS signals have been added, click on ―OK‖ to
navigate to the Measured Signal setup page with all the added Band RMS signals as
shown in the Figure below.
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Figure 211: Measured signals setup – Band RMS Spectra
The Start and Stop frequencies can be edited from the Start and Stop Frequency
columns on this window. The measurement channel can also be edited. The Delete
key can be used to delete any unnecessary signals from this list.
The ―Measure‖ and ―Save List‖ checkboxes work exactly the same as the
corresponding attributes for Order Spectra or FFT Spectra signals.
All Signals
The All Signals tab displays all the signals at one place for the user to view, as shown:
Figure 212: Measured signals setup – All Signals
The user can enable or disable each signal by checking or un-checking the Measure
attribute. The user can also modify the Save / Record attribute for each signal.
The additional attributes with signals, such as Order Tracks and Band RMS Spectra
cannot be edited or viewed from this tab.
Running a test
The following key aspects must be verified before running a test:
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1. The analysis settings are configured correctly. The settings include the
Tachometer settings, Order Analysis settings and FFT analysis settings.
2. The Input channels have been configured appropriately
3. The Measured Signals have been augmented with all desired signals added to
the Measured list and Save/Record list.
4. The tachometer is connected correctly and the physical connections with all
the input channels are appropriately set.
Once the above settings are verified, the test can be run.
Make sure the device is connected, if the device is not connected, then the Connect
button would be enabled. Click on Connect to connect the Spider-80X module to
the EDM.
Once the module is connected, click on Run to start running the test.
Click on Hold to suspend processing at any point of time, this will freeze all the
calculations and the existing displayed signals will ―freeze‖. Click on Continue to
continue the test into the running state again.
The Record button initiates recording of all time stream signals selected for record
in Measured Signals. Pressing the Save button triggers saves all the current block
signals to the Spider Internal flash or the PC. For further information, navigate to
Save and Record Settings in this manual.
Stop completely stops the test and the recorded and saved signals from the Spider
hardware module can be downloaded to the PC.
Display signals
As seen from the previous section, the left hand bottom pane of the EDM default
screen consists of the Live Signals tab which contains all the required signals that
may need to be viewed.
All the signals that have the Measure attribute enabled are displayed here.
The following Figure shows the typical Live Signals tab for an Order tracking test
with all categories of enabled signals.
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Figure 213: Live signals for a typical Order tracking test
The signals are by default sorted according to the type of the signals. When multiple
modules are used, the signals can be sorted according to each module can be set by
right clicking on the Pane and click on ―Sort Signals by Spider module‖.
3D Signals Display
3D signals are of particular importance in Order tracking and enable convenient
analysis by plotting the consecutive blocks of data in the 3rd dimension to analyze
the changes in the block signal. Typically the Z-axis or the Reference axis can be
Time or RPM.
EDM has a capability to plot the signals in 3D by either using time or RPM as the
reference axis. 3D signals can typically be displayed in two different ways:
3D Waterfall Trace is used to display order spectra and order tracks vs. RPM or
time in three dimensions.
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Color Spectrogram is used to display order spectra and order tracks vs. RPM or
time in 2 dimensions using color to represent the magnitude of the signal.
The limits of the 3D waterfall and color spectrogram depend on the Analysis
Parameters such as low and high RPM and max order. The resolution of the plots
depends on the Analysis Parameters delta RPM and delta order. Note that a larger
RPM or order span or a higher resolution will affect the acquisition of the data and
the memory required. Best quality results can be obtained by selecting optimum
resolutions.
Figure 214: Create 3D display
To create a 3D signal plot. Right click on the title of any chart. Click on Other Quick
Window and the options would contain Waterfall Window which creates a 3d
Waterfall plot and a Colormap Window which creates a 3D Spectrogram.
Alternatively, right click on any signal from the live signals that support 3D signals
display and click on 3D waterfall display or the 3D Colormap display.
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Figure 215: Create a 3D Waterfall or 3D Color Map display
Figure 216: Typical 3D waterfall display
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Figure 217: Typical 3D Color Map display
The above figure shows a typical 3D Spectrogram and a typical 3D Waterfall plot.
The Z axis properties can me modified by clicking on the Z-axis line of the chart
which pops up a Z axis setting window.
Figure 218: Z Axis Settings for 3D displays
The Delta time which defines the spacing between two consecutive data frames on
the Z axis can be modified. The Frame Size gives the maximum number of Z axis
points that must be displayed. For e.g. a frame size of 50 can store up to 50 block
signal‘s data and display it to the user.
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Real Time Digital Filter
Real Time Digital Filters can be used to filter a measured signal in real time. Filter
characteristics can be defined by the user to meet the requirements of a specific
application. Real-time digital filters are applied in the data conditioning phase. The
filters are designed with a graphic design tool and then uploaded to the front-end
for real-time calculation. The graphic design tool defines the filter performance
vertical axis with a dB scale. The horizontal axis is defined as relative frequency.
For example, a user might want to look at the energy distribution for a specific band
of frequencies over time instead of for the entire frequency spectrum. This can be
done by creating a band-pass filter and then applying an RMS estimator to the
output of the filter.
The figure below shows a graphical representation of the process used to define a
real time filter in the EDM software. The icon on the left, CH1 represents the native
measured time stream. It is connected to an IIR Filter which computes a signal
named iirfilter (ch1) which is connected to an RMS estimator. The output of the
RMS estimator is a signal named rms(iirfilter(ch1)).
Figure 170. Example of real time digital filter application.
Another example: Perhaps a user wishes to look at the energy in bands from 100 Hz
to 200 Hz and from 1000 Hz to 2000 Hz. This can be done by deriving two output
streams from the native channel 1 and then applying the band-pass filter to each
path as shown in Figure 171.
Figure 171. A Digital Real Time Filter with two output streams.
In another example, you might want to sample a signal at a high rate to capture
high frequency events but may also wish to sample the same channel at a lower rate
to see lower frequency events. This can be done by applying a decimation filter to
the native time stream. The native channel time stream is split into two streams so
the signal from the same channel is recorded at both high and lower sampling rates.
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Figure 172. Example computing high and low sampling rate with a
decimation filter.
The Real Time Digital Filters option includes three types of digital filters: Finite
Impulse Response (FIR), Infinite Impulse Response (IIR) and decimation filters.
For the FIR and IIR filters you can specify: low-pass, high-pass, band-pass or
band-stop filters with several different methods.
This chapter first explains some filter design theory and then introduces filter
operations within the EDM and the Spider hardware.
The goal of filter design is to calculate a series of filter coefficients based on user
specified criteria. The criteria are often described by following variables:
Number of filter coefficients: this is also known as the order of the filter. The
filter order defines how many coefficients are required to define the filter. A lower
order filter consists has fewer coefficients. A low order filter responds faster than a
higher order filter so there are fewer time lags between the input and output of the
filter.
Cutoff frequencies: For low-pass or high-pass filters, only one cutoff frequency is
needed. Band-pass or band-stop filters require two cutoff frequencies to fully define
the filter shape. Figure 173 shows a typical band-pass filter design with the two
cutoff frequencies set to approximately 0.1 and 0.2 Hz.
Stop-Band Attenuation: This specification defines how much of the input signal
is cut out of the output at the rejected frequencies. In theory, the higher the
attenuation the better the filter. The stop-band attenuation is greater than 40 dB as
seen from the highest side lobe just below 0.25 Hz.
Pass-Band Ripple: Ripple is an unavoidable characteristic if a digital filter. It
refers to the fluctuation in the filter shape outside the transition frequencies. If a
very flat filter is required then it can be specified by choosing a very low ripple. In
Figure 173, the ripple is seen in the stop band but no ripple is evident in the passband. Ideally the pass-band should be very flat and some ripple is tolerable in the
stop-band.
Width of transition bands: This refers to the filter shape between a band-pass
and a stop-band region. Ideally this transition band should be very small. However,
a very narrow transitional band requires a higher order filter which affects the filter
response time and can also affect ripple. The transition bands are between 0.05 to
0.1 and 0.2 to 0.25.
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Figure 173. Filter design shows cutoff frequencies, ripple, band stop
attenuation.
In most cases filter design includes making tradeoffs between minimizing the filter
order, ripple, transition band-width, and response time. Not all can be satisfied at
the same time. Filter design can be an iterative process and experience is helpful.
FIR Real Time Digital Filters
Finite Impulse Response (FIR) filters have an impulse response that lasts for a
finite duration of time. Infinite Impulse Response(IIR) filters have an impulse
response that is infinite in duration. The FIR filter‘s finite response is due to a lack
of feedback paths. FIR filters offer several advantages over IIR filters including:
 A completely constant group delay throughout the frequency
spectrum. Group delay refers to the time delay between when a signal
goes into the filter and when it comes out. Constant group delay
means that an input signal will come out of the filter with all parts
delayed by the same amount and with no distortion.
 Complete stability at all frequencies regardless of the size of the filter.
FIR filters also have some disadvantages:
 The frequency response is not as easily defined as it is with IIR filters
 The number of coefficients required to meet a frequency specification
may be far larger than that required for IIR filters.
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A digital filter can be understood by considering the equation which defines how
the input signal is related to the output signal:
𝑦 𝑛 = 𝑏0 𝑥 𝑛 + 𝑏1 𝑥 𝑛 − 1 + ⋯ + 𝑏𝑁 𝑥 𝑛 − 𝑁
Where x[n] is the current input signal sample, x[n-1] is the previous signal sample
and x[n-N] is the last sample in the series. The series multiplies the most recent
N+1 samples with the associated N+1 filter coefficients. y[n] is the current output
signal and bi are the filter coefficients. The number N is known as the filter order;
an Nth-order filter has (N + 1) terms on the right-hand side. N+1 filter coefficients
are also referred to as ―taps‖.
This equation illustrates why a higher order filter has a slower response time. It
takes more samples and therefore more time for an event to work its way through
the series until the output is no longer affected by the event. A lower order filter has
fewer coefficients and therefore a faster response time.
The previous equation can also be expressed as a convolution of the filter
coefficients and the input signal, specifically:
𝑁
𝑦𝑛 =
𝑏𝑖 𝑥 𝑛 − 𝑖
𝑖=0
The Impulse Response of the filter shows how historical data affects the current
filtered value. The longer the impulse response, the more the older data will affect
the current filtered value. To find the impulse response we set
𝑥 𝑛 = 𝛿[𝑛]
Where δ[n] is the Kronecker delta impulse. The equation below shows that the
impulse response for an FIR filter is simply the set of coefficients bn, as follows
𝑁
𝑕𝑛 =
𝑏𝑖 𝛿 𝑛 − 𝑖 = 𝑏𝑛 𝑓𝑜𝑟𝑛 = 0 𝑡𝑜𝑁
𝑖=0
FIR filters are stablebecause the output is a sum of a finite number of finite
multiples of the input values that can be no greater than 𝑁
𝑛=0 𝑏𝑛 times the largest
value appearing in the input.
Data Windows FIR Filters
In the academic world, hundreds of methods are available to design FIR filters to
meet various criteria. EDM includes the most popular filter design methods: Data
Window and Remez. Both methods are discussed below.
The Data Window FIR Filter Design method is the easiest to understand. The
name "Window" comes from the fact that these filters are created by scaling a
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sinc(SIN(X)/X) function with a window such as a Hanning, Flat Top, etc. to
produce the desired frequency effect.
Figure 174Sinc function is the Fourier transform of a square shape.
A data window FIR filter is generated by starting with an ideal ―brick-wall‖ shaped
filter; that is a filter with vertical edges or zero transition band widthas shown on
the left in Figure 174. The brick-wall filter is specified by its cutoff frequencies and
it has band-pass amplitude of 1 and stop band amplitude of zero. The problem with
the ideal brick-wall filter is that the time response oscillates forever and it requires
an infinite number of filter coefficients.
This ideal filter can be modified by applying a data window to force the time
response to decay in a finite amount of time. Of course this degrades the ideal
shape of the brick-wall filter. It introduces ripple, increases the transition band
width and decreases the stop band attenuation but it allows the filter to be defined
by a finite number of filter coefficients. Filter performance can be modified by using
different data windowing functions that offer tradeoffs between filter order and
response time. The user must choose these settings during the filter design.
Figures below show a comparison of various data window choices for the same filter
settings. In all cases the low and high cutoff frequencies are 0.1 and 0.2 relative to
the sampling frequency. The number of filter taps is 67.
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Figure 175: The Hanning window
Figure 176: The Hamming window
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Figure 177: The Flattop window
Figure 178: The Uniform window
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Figure 179: The Kaiser Bessel window
Figure 180: The Blackman window
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As shown in the pictures, different windows produce different filter performance,
i.e., different attenuation of the main lobe and side lobes. The best data window is
the one that best suits your specific application.
Remez Filters
The Remez Filter is a different method for designing an FIR filter. It is more
computationally intensive than the data window method. A Remez filter is
generated with iterative error-reducing algorithms designed to reduce the passband error. In addition to allowing stop-band ratio and frequency definition, the
Remez filter also allows the "Ripple Ratio" to be defined as a user specified
parameter.
The figure shows an example of a filter design using the Remez method in the EDM
software. The low and high cutoff frequencies are 0.1 and 0.2 relative to the
sampling frequency. The number of filter taps is 67.
Figure 181. Remez FIR Filter design dialog.
The software is intelligent enough to automatically calculate the total FIR filter
length (number of taps) based on these criteria. For example if the user asks for
very high attention, very small ripple or very sharp transition band, the filter length
will go very high. The user must make tradeoffs between these parameters so that
appropriate filter length can be generated and used.
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IIR Real Time Digital Filters
Infinite impulse response (IIR)filters have an impulse response that decays
very slowly and theoretically lasts forever. This is due to the fact that the filter input
includes the measured signal and also the filter output creating a feedback path
which results in the infinite impulse duration. This is in contrast to finite impulse
response filters (FIR) which have fixed-duration impulse responses.
The design procedure for IIR filters is somewhat more complicated than FIR filter
design because there is no direct design method like the data window method for
FIR filters. IIR filters are typically designed by starting with an ideal analog filter in
terms of the frequency response characteristics such as the Chebyshev, Butterworth,
or Bessel filter. Then the analog filter is converted into a digital filter using a
method known as the Bilinear transformation or the impulse invariance method.
An IIR digital filter can be understood by considering the equation that defines how
the input signal is related to the output signal:
𝑦 𝑛 = 𝑏0 𝑥 𝑛 + 𝑏1 𝑥 𝑛 − 1 + ⋯ + 𝑏𝑝 𝑥 𝑛 − 𝑃 − 𝑎1 𝑦 𝑛 − 1 − ⋯ − 𝑎𝑞 𝑦 𝑛 − 𝑄
Where P is the feed-forward filter order, 𝑏𝑖 are the feed-forward filter coefficients, Q
is the feedback filter order,𝑎𝑖 are the feedback filter coefficients,x[n] is the input
signal and y[n] is the output signal.
The previous equation can also be expressed as a convolution of the filter
coefficients and the input signal.
𝑄
𝑃
𝑦𝑛 =
𝑏𝑖 𝑥 𝑛 − 𝑖 −
𝑖=0
𝑎𝑗 𝑦 𝑛 − 𝑗
𝑗 =0
Which, when rearranged, becomes:
𝑄
𝑃
𝑎𝑗 𝑦 𝑛 − 𝑗 =
𝑗 =0
𝑏𝑖 𝑥 𝑛 − 𝑖 𝑖𝑓𝑤𝑒𝑙𝑒𝑡𝑎0 = 1
𝑖=0
To find the transfer function of the filter, we first take the Z-transform of each side
of the above equation, where we use the time-shift property to obtain:
𝑄
𝑃
−𝑗
𝑏𝑖 𝑧 −𝑖 𝑋(𝑧)
𝑎𝑗 𝑧 𝑌(𝑧) =
𝑗 =0
𝑖=0
We define the transfer function to be:
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𝑌(𝑧)
𝐻 𝑧 =
𝑋(𝑧)
𝑃
−𝑖
𝑖=0 𝑏𝑖 𝑧
𝑄
−𝑗
𝑗 =0 𝑎𝑗 𝑧
The transfer function gives the frequency response that relates the input to the
output in terms of magnitude and phase.
Various analog filter types can be used as the basis for the IIR filter. The
Butterworth Filter results in the flattest pass-band and contains a moderate group
delay. Below are examples of Butterworth low-pass and band-pass filters.
Figure 182. Butterworth band-pass filter.
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Figure 183. Butterworth low-pass filter.
The Chebyshev Type I Filter results in the sharpest pass-band cut off and contains
the largest group delay. The most notable feature of this filter is the significant
ripple in the pass-band magnitude. A standard Chebyshev Type I Filter's pass-band
attenuation is defined to be the same value as the pass-band ripple amplitude.
Below are examples of Chebyshev Type I band-pass and high-pass filters.
Figure 184. Chebyshev type I band pass filter.
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Figure 185. Chebyshev type I high pass filter.
The Elliptic Filter contains a Chebyshev Type I style equiripple pass band, an
equipped stop band, a sharp cutoff, high group delay, and the greatest possible stop
band attenuation. Below are examples of 7th order Elliptic low-pass, band-stop
filters.
Figure 186. Elliptical low-pass filter.
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Figure 187. Elliptical band stop filter.
Applying Filters
When creating a new FFT test, check the FLT box to enable Filters parameters.
When the FLT box is checked, the real time digital filter will be applied to all
available input channels.
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Figure 188. Enabling Filters in the New Test Wizard
Go to Setup->Measured Signals. The last column is filter selections. There are
FIR(Window), FIR(Remez), and IIR filters. Only one type of filter can be applied at
a time. In the same test, different channels can have different types of filters. Filters
are only applicable to time streams.
Figure 189. Measured Signal Setup – Filters
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It is important to keep in mind that the cutoff frequencies are relative to the
sampling rate, when the sampling rate changes, the cutoff frequencies in absolute
Hz will be changed. For example, when the sampling rate is 1000 Hz, a 0.1 cutoff
frequency means 100 Hz. If the sampling rate is changed to 102.4 kHz, the cutoff
frequency will be moved to 1.024 kHz.
Automated Alarm Limit Test
The Automated Alarm Limit test function allows the Spider front-end to conduct
automated limit checking for time or frequency signals. The function is supported
in both PC-tethered mode and Black Box mode.
The Spider compares the limits to the live measured signal in real-time, after every
single frame of measurement. If the limits are exceeded, the Spider takes the
appropriate actions based on the user setup.
Limiting signals are created and edited using EDM on the host PC. There are four
elements in a limiting test: the signals being tested, upper or lower limits applied,
testing schedule and testing log. In most cases it will be easy to generate automated
alarm responses when the limits are exceeded. Alarm responses include sending
email notifications, beeping, screen flashing and controlling the current test.
In every type of test, limits can be bound to time stream signals, block signals and
spectrum signals. Users can define a high limit and a low limit. When a live signal
exceed a limit, a predefined event will be triggered as an alarm. Each limit line can
have up to 64 segments and there can be a maximum of 64 limit signals.
A testing schedule is used to automatically control the limit checking test. The
testing schedule defines various operations to automate the process. For example
the testing schedule can tell the instrument when the limit checking will be turned
on, when it will be turned off and for how long the test will be conducted.
To record the events of the test, a Testing Log and a summary report are needed.
The Testing Log records the important events in chronological order, including
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whether the limits have been exceeded. The Summary Report provides the status of
the limiting checks since the beginning of the test.
When the limit signal is exceeded, a user defined limit alarm event will be triggered.
These can include audible beeps, signal saves, send email messages etc.
To summarize: An automated limit checking test requires the following building
blocks:





At least one test signal
At least one limit signal applied to the measured signals
A testing schedule
A testing log and summary report
A setup for the limit alarm events
Testing
Schedule
Compare the signals and
their limits in runtime
Alarm Event
Setup
Setup
Testing Log
Summary
Report
Beep, send message to Host
PC etc.
Compare the signals and
their limits in runtime
Events and report
Figure 190. An Illustration of the Automatic Testing Process
Apply Alarm Limits on EDM
Limiting and alarm function only works with the master module in a high-channel
count system. This limitation doesn‘t affect other modules measuring signals. In an
FFT test, right-click the signal name and then click Apply Alarm Limits to setup
limits parameters. Users can also decide here if the limit lines will be displayed with
the signals.
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Figure 191. Apply Alarm Limits
On the alarm limits list, click Add Limit to add a new limit to the list.
Figure 192. Add Limit
Check the signals you want to add limits to. Press OK to return to the Apply
AlarmLimits main page. Then press Edit Limit to define the amplitude of the
limit lines. Remember that the limit line can have as many as 64 segments. By using
Add Point/Remove Point, the number of segments can be adjusted.
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Figure 193. Add Limit Signal List
Figure 194. Add Limit Signal List
In the signal preview window, the solid red line is the limit and the blue line
represents the live signal.
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Figure 195. Edit Limit for a time signal
Figure 196. Edit limit for a spectrum signal
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Limit configurations can be saved as data files. Press Export to save the current
limit to a data file. Press Import to load a data file to use as a limit. The
Import/Export function can save a great deal of time when similar units will be
used for different tests.
Customize Event Action Strings and Its Application in Limit Checking
The user can customize a string to identify an event that corresponds to a specific
limit check. These strings will be shown on the Runlog display window or report.
The customized strings will be passed from EDM to the Spider devices during the
test initialization phase. The Spider devices will send the strings back when certain
events occur.
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Figure 197. Runlog Event Strings
Users can set custom message strings to be logged by the Runlog when a limit is
exceeded; these strings can be defined through the edit box. For instance, the user
can set messages such as Ch1 Aborted or Sensor 2 Alarm Exceeded for their
respective events.
Figure 198. An Example of Event Strings
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Figure 199. A Customized Event String in the Runlog
Limit Related Settings in Run Schedule and Event Action Rules
Most limit function applications rely on the Run Schedule and the Event Action
Rules. Here we will only deal with the limit settings, information on the other topics
can be found elsewhere in this manual. Multiple events can be triggered when a
limit is exceeded by simply adding them to the list of actions.
Figure 200. Limit Exceeded Events
In the black-box mode, A Limit Check On event must be inserted into the schedule
to enable the limit. After the test is uploaded to the front-end there is no way to
enable the limit.
A limit can be removed from a signal by right clicking it and selecting the option to
remove it. Note that active limits may not be displayed if the display option is not
checked.
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Here is an example of an exceeded limit triggering a flashing screen and a beep.
(Note the lower right-hand corner.)
The software is designed with extreme flexibility so that various ―actions‖ can be
taken besides flashing the screen or beeping. Sending Socket message is a very
powerful tool to communicate with other software applications on the same
network. For example a temperature chamber application running on a Linux
environment can receives the ―Socket Message‖ from EDM application if a certain
vibration limit exceeded.
EDM Cloud is server-based web software that can process the same event action
messages described above. Please refer to the manual for EDM Cloud regarding this
function.
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Shock Response Spectrum Analysis
A Shock Response Spectrum (SRS) is a graphical presentation of a transient
acceleration pulse‘s potential to damage a structure. It plots the peak acceleration
responses of a bank of single degree-of-freedom (SDOF) spring, mass damper
systems all experiencing the same base-excitation as if on a rigid massless base.
Each SDOF system has a different natural frequency; they all have the same viscous
damping factor. A spectrum results from plotting the peak accelerations (vertically)
against the natural frequencies (horizontally).An SRS is generated from a shock
waveform using the following process:
 Specify a damping ratio for the SRS (5% is most common)
 Use a digital filter to model an SDOF of frequency, fn and damping Ξ.
 Apply the transient as an input and calculate the response acceleration
waveform.
 Retain the peak positive and negative responses occurring during the
pulse‘s duration and afterward.
 Select one of these extreme values and plot it as the spectrum
amplitude at fn.
 Repeat these steps for each (logarithmically spaced) fn desired.
The resulting plot of peak acceleration vs. spring-mass-damper system natural
frequency is called a Shock Response Spectrum, or SRS.
Figure 201. Illustration of a multi-degree of freedom system model used to
compute SRS.
An SDOF mechanical system consists of the following components:
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 Mass, M
 Spring, K
 Damper, C
The natural frequency, Fn, and the critical damping factor, Ξ , characterize a SDOF
system, where:
𝑓𝑛 =
𝜉=
1 𝐾
2𝜋 𝑀
2 KM
For a light damping ratio where Ξ is less than or equal to 0.05, the peak value of the
frequency response occurs in the immediate vicinity of fnand is given by the
following equation, where Qis the quality factor:
𝑄=
2𝜉
Any transient waveform can be presented as an SRS, but the relationship is not
unique; many different transient waveforms can produce the same SRS. The SRS
does not contain all of the information about the transient waveform from which it
was created because it only tracks the peak instantaneous accelerations.
Different damping ratios produce different SRSs for the same shock waveform.
Zero damping will produce a maximum response while high damping will produce
a flatter SRS. The damping ratio is related to the "quality factor", Q, which can also
be thought of as transmissibility in the case of sinusoidal vibration. A damping ratio
of 5% (Ξ=0.05) results in a Q of 10. An SRS plot is incomplete if it doesn't specify the
document the damping factor (or Q).
Frequency Spacing of SRS Bins
An SRS consists of multiple bins distributed evenly in the logarithmic frequency
scale. The frequency distribution can be defined by two numbers: a reference
frequency and the desired fractional octave spacing, such as 1/1, 1/3 or 1/6. (An
octave is a doubling of frequency.) For example, frequencies of 250 Hz and 500 Hz
are one octave apart, as are frequencies of 1 kHz and 2 kHz.
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Figure 202. Full octave filter shape.
The proportional bandwidth display is very useful for analyzing a variety of natural
systems such as the human response to noise and vibration. Many mechanical
systems exhibit behavior that is best characterized by proportional bandwidth
analysis.
To gain finer frequency resolution, the frequency range can be divided into
proportional spacings that are a fraction of an octave. For example, with 1/3 octave
spacing, there are 3 SDOF filters per octave. In general, for 1/N fraction octave,
there are N band pass filters per octave such that:
𝑓𝑐𝑗 +1 = 𝑓𝑐𝑗 ∗ 21/𝑁
Where 1/N is called the fractional octave number and the reference frequencyis
simply the lowest desired frequency, fc1. With the reference frequency and fractional
octave number established, the frequency distribution over the whole frequency
range is determined.
Measured Signals in SRS
The measurement quantities available to the Spider SRS test are: time stream of
each channel (raw data), block captured time signals and three SRSs of each
channel.
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Figure 203. Measurement Quantities in SRS
Time streams: this is the same as any other applications on the Spider. Time
streams are always available for viewing and recording. It is a very useful tool for
observing if the input signals are in the valid range or not. The recorded sine wave
can also be used for further post-processing.
Block time signals: These are the block captured signals that are used for SRS
analysis. Acquisition Mode will control how the block time signals are acquired.
SRS: Shock Response Spectra will be calculated for each block of time signals. The
engineering units of the spectrum are determined by the sensor units specified for
the input channel. The spectra are often denoted as three types: Maximum Positive
spectrum; Maximum Negative spectrum and Maximum-Maximum spectrum.
Maximum Positive Spectrum: This is the largest positive response due to the
transient input, without reference to the duration of the input.
Maximum Negative Spectrum: This is the largest negative response due to the
transient input, without reference to the duration of the input.
Maximax Spectrum: this is the envelope of the absolute values of the positive
and negative spectra. It is the most often used SRS data type. The log-log Maximax
is the universally accepted format for SRS presentation.
SRS Analysis Parameters and Synthesis Parameters
All of the SRS analysis test parameters can be found in Test Config->Analysis
Parameters. FFT analysis parameters are defined in the same way as other FFT
tests. SRS parameters include:
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Figure 204: SRS Analysis Parameters and Synthesis Parameters
Reference Frequency: defines the reference frequency of the SRS spectrum.
SRS Type includes the Maximum Max, the Positive Max, and the Negative Max.
Fractional Octave Number is chosen from 1/1, 1/3, 1/6, 1/12, 1/24, 1/48.
Low Frequency: defines the lowest frequency boundary of the SRS spectrum.
High Frequency: defines the highest frequency boundary of the SRS spectrum.
Damping Ratio (%): defines the damping ratio as a percentage.
Q (Quality Factor) is a dimensionless parameter that describes how underdamped an oscillator or resonator is, or equivalently, characterizes a resonator's
bandwidth relative to its center frequency.
Wavelet Window Type is the windowing function available from Sine, Hann,
Exponential, and Rectangular.
Synthesis has four available synthesis including Pyroshock, Minimum
Acceleration, User Defined Duration, and Mil-Std810-F Standard.
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Sweep Sine FRF
Introduction
Sweep Sine FRF is a shaker diagnosis tool that allows the user to manually control
the sine tone and drive voltage. It also has a built-in close loop control so that it can
be used as a very simple sine controller.
Figure 205. New Test Wizard
When the New Test is called, if the Include Closed Loop Controlcheckbox is
checked, then the test will ask you to set up the profile so the closed loop control can
be conducted. With closed loop enabled, the system is actually a simple sine
vibration control system. If this box is not checked, the system will run in the openloop mode.
The Sweep Sine FRF test allows the output sine wave to be manually controlled by
the user. The controllable parameters include frequency, amplitude, sweep rate,
frequency limits and direction. When being manually controlled, the sine output is
not under closed-loop control as it is during a regular swept-sine test. Closed-loop
control can also be turned on to function as a simple sine controller.
The sweep parameters are set under the control panel. This replaces the run
schedule used in the regular Sine mode.
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Figure 206. Sweep Sine FRF Control
The Drive Mode switches between Freq. Scanning mode, which outputs a sine
sweep, and the Fixed Freq. mode, which outputs a fixed frequency.
Figure 207. Drive Mode
The Close Loop button turns on closed-loop control. The output drive level will be
adjusted so that the input control signal matches the profile. The profile is set under
the Profile and Schedule section of the Test Configuration window, just like the
normal Sine test.
To enable the close-loop test in Sine Oscillator, check the box, Include Closed
Loop Control, below when a new test is created:
In Closed-Loop control, a testing profile must be defined:
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Figure 208. Test profile
When in closed-loop control mode, pressing Open Loop will revert back to the
manual control mode.
General Operation
Set and Change the Drive Voltage
People use the Sine Oscillator function to test their shaker‘s performance. Most
often, the user wants to set a specific drive voltage at a certain frequency. To set the
initial drive voltage, you can use the Set button on the control panel, or use F11/F12
key on the keyboard, or click on the small buttons with numbers as shown below:
The system will ramp up or down to the target voltage instead of creating a sharp
step. Therefore, it will take some time to settle the drive voltage.
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The Drive plot displays the amplitude and frequency of the current drive output.
The following plot shows the increase in the control signal measured from a shaker
while the drive voltage is gradually increased by pressing the F12 button.
Set and Change the Frequency
To change the frequency of drive signal, click the Set button in the control panel, or
click on the small buttons with numbers, or use keyboard keys F10/F9.
When frequency is changed, the drive will immediately jump to the target
frequency without ramping down the signal.
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The signal Frequency_His(t) is the time trace of the frequency. The picture
below shows the frequency trace when the user pressed the 10Hz up and down
buttons.
The picture below shows a sine wave that was sweeping up and then down and then
placed on-hold.
Calculate the Total Harmonic Distortion
To calculate the Total Harmonic Distortion (THD), press the Calculate THD button
on the control panel while in the Fixed Frequency testing mode.
The THD Display can be found by right clicking on the time stream signal:
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Here is a typical THD display:
Make it Sweep
Instead of running in the fixed frequency mode, the sine output can sweep. In
Sweep Sine FRF, set the Drive Mode to Swept Sine:
Then make sure the sweeping parameters are set up correctly on the second tab of
Control Panel:
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Pressing the Sweep button on the Control Panel will make the output sweep.
Display the Acceleration, Velocity or Displacement of the Spectrum
As in any controlled Sine test, you can display the spectrum value in velocity or
displacement as well as acceleration. To make the change, simply right click on the
signal plot and select the appropriate quantity.
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Sine Reduction
Introduction
Sine Reduction allows you to ―slave‖ a digital signal analyzer (DSA) to a vibration
control system (VCS) to gain more processing channels for a swept sine test. The
Sine Reduction software runs on the DSA; no changes to the VCS are required. The
two instruments are synchronized by the controller‘s COLA (constant output level
amplitude) signal. The COLA is a constant voltage sine wave that tracks the Drive
signal in frequency during a Sine test.
A Typical Test
Here‘s a typical test system using Sine Reduction. The Spider-81 VCS provides eight
channels of input. By connecting its Output 2 (the COLA) to the Channel 1 input of
a Spider-80X DSA module running Sine Reduction, the combined VCS system
provides 15 input channels all running the same tracking filters in perfect
synchronization.
Figure 209. An Example of Connection
Configuration on EDM
To configure the COLA output channel on a Spider controller, Go to Config.>Miscellaneous->Second Output tab and set it to COLA Type 1: Constant
Amplitude Sine; and set the amplitude to1V.
If you are using another make of controller, please make sure its COLA channel is
set to sweep at the Drive frequency with fixed amplitude.
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Figure 201: Setting the COLA signal parameters on the Spider-81 VCS
To set up the Sine Reduction on the analyzer side, first create a sample test using
EDM.A sine reduction test can be created from the New Test tab or the option of
the New Test Wizard.
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Figure 202. Create a Sine Reduction test on the Spider-80X DSA
Go to Input Channels table to set the channel 1 Channel Type to COLA. Each
Sine Reduction test has only one COLA channel. In this example, the first is used,
but any one of the inputs may be as the COLA input channel.
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Figure 210. Channel Table Setting for Sine Reduction Test
Sine Reduction parameters can be found in the Test Parameters tab under Test
Configuration. All parameters should match those set on the sine controller. The
COLA Amplitude is determined by the COLA output value of the controller. The
Low Frequencyand High Frequencyparameters must match the test profile of
the sine controller.
Figure 211. Sine Reduction Parameters
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When all Sine Reduction parameters are properly set, press the Run button to start
the Sine Reduction test. The sine controller can be started before or after starting
this DSA test.
Figure 212. A Typical Sine Reduction Test
In a Sine Reduction test, the user can easily set up FRF, Transmissibility and other
measurements identically to the way they are set up on the VCS.
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EDM Keyboard Shortcuts
Command
Help
Run, Start
Pause, Hold
Continue
Stop
Record
Save Sigs
New Test
Find Test
Keys
F1
F2
F3
F4
F5
F6
F7
Ctrl-N
Ctrl-F
Copy image
Ctrl-C
Add Annotation
Ctrl-A
Save Window Signal
Ctrl-S
Cache Signal
Ctrl-K
Test Config
Global Setting
New window
Auto/Fix all
Ctrl-T
Ctrl-G
Ctrl-W
Ctrl-Q
Un-Zoom
Ctrl-Z
Scroll plots(left, right)
Scroll plots(up, down)
Left and right
keys
Up and down
keys
Cursor on/off
Spacebar
Time Stream
Time Blocks
Spectrum
Frequency Response
Function
Composite
Digital I/O
Channel Status
Customize
Save Active Window
as…
Connect
Disconnect
Ctrl+1
Ctrl+2
Ctrl+3
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Description
Open a Help file
Start the test or measurement
Pause or hold the test
Continue the test
Stop the test
Record the time stream
Save signals in the list
Create a new test
Find test (open find test tab)
Copy an image of the active window to the
clipboard
Add annotation to the active window if there is
no cursor. Add annotation to the cursor
location if there is a cursor.
Save the signals in the active window
Cache signals in the active window. If there are
many signals in the active window, cache all of
them.
The cached signals will be listed in the cached
pane (in the lower left corner).
Configure current test
Access Global settings
Open an overlaid new empty window
Toggle Auto scale and fix scale for all windows
Zoom back to the previous scaling range for
the active window
Move the plot scales to the left or right for
about 1/20 of the active window
Move the plot scales to the top or bottom for
about 1/20 of the active window
Enable or disable the cursor on the active
window
Ctrl+4
Ctrl+5
Ctrl+6
Ctrl+7
Ctrl+Shift+I
Ctrl+Shift+S
Ctrl+Shift+C
Ctrl+Shift+D
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Installing the Engineering Data Management Software (EDM)
To install the desktop software on your PC, insert the included CD-ROM into your
CD drive. If the Welcome Screen does not automatically open, you can run the
Setup.exe file on the root level of the CD.
Figure 213: Welcome Screen for EDM Installation CD.
EDM requires MSSQL server 2008 R2 version or later.
Microsoft SQL Database Server Installation
EDM requires an SQL database server. Currently, EDM software supports
Microsoft SQL Server 2008 R2 and MySQL 5.0.67. If neither of the SQL database
managers is installed, the EDM installer will prompt the user to install MSSQL
before installing EDM. If MSSQL is already installed, the installation of database
software will be skipped and the existing database software will be used with EDM.
If MySQL is detected, a selection can be made to install and use MSSQL or to
continue using MySQL.
The flow chart below illustrates the steps of EDM and database server setup.
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Figure 214: SQL Server Installation Flow Chart
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Figure 215: SQL Server Installation Wizard
The following instructions describe how to install the MSSQL Server Software.
MSSQL is separate software licensed for use with EDM. It is used to manage the
database that stores route and measurement data.
The EDM installer will prepare the necessary files for MSSQL Server Installation
and will begin installing MSSQL.
Figure 216: EDM Extracting MSSQL Installation Files
The message box and the command line window below indicate that the MSSQL
installer has been initialized successfully. Do not close any windows during the
setup process.
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Figure 217: MSSQL installation initialization
Figure 218: MSSQL Installation Wizard Launching
The Installation Wizard will prepare support files for troubleshooting and Help
menus after installation.
Figure 219: MSSQL Support Files Setup
The Wizard is configured to install MSSQL with default options that ensure it works
with EDM. There are no settings that need to be specified by the user.
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Figure 220: MSSQL Installation in Progress
When the database server is successfully installed the EDM installation will begin.
The following section discusses the installation procedure for EDM.
Note: Having a computer and a user account with the
same name can cause login errors. If problems are
encountered logging into MSSQL, verify that the computer
name does not match any user account. To check the
computer name: right-click on My Computer and select
Properties. The computer name will be on the first page. To
check the user name: right-click on My Computer and
select Manage. Expand Local Users and Groups and click
on Users to see all user accounts.
Windows Installer 4.5 is a prerequisite for MSSQL
installation. The system must be rebooted after Windows
Installer 4.5 is installed.
Folder may not have the advanced options of encryption or
compression enabled.
When EDM fails to connect to the MSSQL server database,
deleting ―EDM.database.dll.config‖ might solve the
problem.
EDM versions newer than Version 3.1.5.1 use MSSQL instead of MySQL. However,
newer EDM versions are still backward compatible with MySQL for users
upgrading from older versions (Version 3.1.5.1 or older).
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This means that users who are familiar with MySQL can keep using the MySQL
database. Switching to Microsoft SQL Server is not mandatory. The MySQL
installer is not available in versions higher than 3.1.5.1.
EDM Software Installation Wizard
The EDM installer will launch immediately after completing the installation of the
MSSQL database management software. To install the Engineering Data
Management (EDM) software without installing an SQL server, click Install EDM
Software (version X.X.X.X) from the EDM Installation screen to launch the
Installation Wizard.
Important: SQL database software is necessary for EDM
to operate. The supported database managers are MSSQL
(recommended and installed by default) and MySQL. If
MySQL is preferred or currently used for EDM database
management, refer to Appendix 3.
Figure 221: EDM Installation Wizard
Click Next to begin the installation process.
Review and accept the license agreement and click Next.
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Figure 222: EDM License Agreement Acceptance Page
To install EDM a valid license key is required. If the default location does not
contain your license key, browse for the correct folder. Once the license key has
been specified, press Next.
Figure 223: License Key Directory Page
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The Software Renew Periodis the time period during which the software can be
upgraded. The Software Activation Periodis the time period during which the
software is operational and can be used.
Where is My License Key?
There are two ways to obtain your EDM software License Key.
When you received your Spider module from Crystal Instruments, you should have
received an automated email message with shipping information, your EDM license
key file, and your product serial number. The license key file is a file that contains
the extension .LIC.
If you have not received this email message, or do not have your license key, you
will need to obtain the license key file from the Crystal Instruments support website:
http://www.go-ci.com/support.asp. If you do not have a password, call Crystal
Instruments tech support and they will send it to you. (Your login username is the
product serial number).
It is a good idea to store the License Key, the serial number
of your instruments, and your password somewhere secure
where you can always find them. You will need this
information to log onto the CI Technical Support Site for
assistance and updates. If they are lost, please call CI
Technical Support at (408) 986-8880.
Continue the installation process after obtaining the License Key files. Select the
features to be installed.
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Specify the installation directory and press Next. The default directory is
C:\Program Files\Crystal Instruments\EDM.
Figure 224: Installation Directory Page
If desired, specify a preferred location for Data Files, CSA Projects, Arbitrary Signal
files, and Limit Collection files. Press Next to continue.
Figure 225: EDM Default Save Location Page
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Specify the Start Menu folder name and press Next.
Figure 226: Programs Folder Title Page
Select your preferences for Shortcuts, Default Units, Default Language, Paper Size,
and Multiple Module support. These settings can be changed later in the EDM
Settings menu. Press Next.
Figure 227: EDM Default Settings
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Review the installation settings. Click Back if changes are necessary. Click Next if all
settings are correct. The Installation Wizard will then set up EDM according to the
settings you have chosen.
Figure 228: Installation Summary Page
Click Finish to exit the EDM installer.
Figure 229: Completed Installation Page
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Using EDM App
The EDM App for iPad is a software program designed for vibration control and
real time data processing on the iPadmanufactured by Apple Inc..It supports FFT,
Random,Swept Sine, and Shockvibration control tests that are uploaded by the
EDM PC software. The EDM App for iPad also createstests directly on the iPad.
The Spider-20/20E only support DSA function mentioned below, and all VCS
related functions will be available on other Spider platforms.
The user can adopt one of the following two scenarios to run a test on the Spider
hardware platform:
Normal Configurable Mode:The EDM App for iPad can create and edit its own
tests and run those tests on Spider front-ends. In this process the EDM PC software is
not required. The tests created and run by the iPad have reduced functions compared
to the EDM PC version.
Black Box Mode:The VCS and DSA tests can be uploaded via EDM PC software.
The test typesincludeFFT DSA,Random, Sine-on-Random, Random-on-Random,
Swept Sine, Resonance Search and Dwell.Afterthe PC is disconnected from the
Spider, the Spider can run in Black Box mode. While running in Black Box mode, the
EDMApp for iPad can access tests on the Spider, view signals, and control tests. In
this case the test setup such as profile or channel table cannot be changed by the iPad
app.The control options in the app include reset average, next entry button, level
adjustments,anON/OFF switch for abort checks, a closed loop and schedule timer
apart from Run, Pause, and Stop buttons.
The benefit of running theiPad in Black Box mode is that the test can be any
configuration as long as the EDM VCS (PC version) supports it. For example, tests
as complex as RSTD or Sine-on-Random are all be supported. Up to 8 input
channels are supported. The drawback of this approach is that the EDM App for
iPad will not be able to edit or change any parameter settings.
Through a direct wireless connection between your iPad and any Spider units on
the wireless network, the EDM App for iPad allows engineers to monitor and
control test settings and measurements, flip through existing measurement setups
and past measurements runs, or create new test configurations from scratch. A
wide range of display types and layouts offers online data viewing and real time
interaction.
Using the iPad brings additional freedom to test engineers, making it possible to
control any shaker table in the lab on or near the test object while walking around
freely during a test, or monitoring signals on the iPad in real time.
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The EDM App for iPad is the only software required to run the Spider hardware.
Screen shots together with testing status are emailed as testing report to the
recipients with one command.
The EDM App for iPad software only runs one Spider front-end at a time. From the
EDM App, the user can select one of the Spider front-ends detected through its
wireless network. TheiPad can be disconnected or reconnected to any valid frontend.
Each Spider front-end has its own access control passwordto prevent unauthorized
access on the wireless network.
English, Japanese and Simplified Chinese are available. The language can be
switchedthrough the iPad language environment without reinstalling the software.
All types of Spider platforms are supported by this iPad application.
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Figure 230. All supported Spider's
The new design of hardware and software completely eliminates the reliability issue
caused by a PC in the real-time control and data acquisition application.
It is ideal for production tests or long duration tests. It is ideal for data acquisition
applications that run without people in attendance.
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Figure 231. Connection topology
Hardware devices connected to the local area network will be identified by the IP
addresses.
For Spider-81C or Spider-20 which has a built-in Wifi router, the iPad will be
directly communicate with these front end devices without going through external
router.
Figure 232. iPad connects to Spider-20 through wireless
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Installing the iPad Software
The EDM apps can be downloaded from the Apple Store at the following address
https://itunes.apple.com/en/app/wireless-edm/id496468252
Figure 233. EDM App in App Store
The EDM iPad App is available on the Apple App Store that is included on all iPads.
It is easiest to find the app by searching ―Crystal Instruments‖.
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Figure 234. Download EDM App from App Store on the iPad
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Control the Spider from the iPad
Network Connection
In order to connect, the iPad on its wireless connection must be on the same
network as the Spider on its wireless/wired connection.
Spider-20 and Spider-81C are equipped with built-in wireless connection. Because
they are wireless device themselves, the App on the iPad can establish a point-topoint wireless connection with Spider-20 and Spider-81C. No external routers are
required in this connection.
Following are the factory settings of Spider-20 and Spider-81C.
WI-FI ID: Spider_SERIAL_No
WI-FI Password: [BLANK]
DHCP Gateway: 192.168.1.10
Subnet Mask: 255.255.255.0
DHCP Server: Enabled
For the wired Spider device such as Spider-80X, Spider-81, and Spider-81B, the
best way to do this is to use a wireless access point connected directly to the Spider.
The iPad then connects to it through Wi-Fi. If the access point has a DHCP server, it
should be enabled so that all devices automatically get a configured IP address.
On the iPad, the wireless setting is configured under Settings->Wi-Fi. If the Spider
or the wireless router has DHCP server enabled, user should use DHCP IP address
on the iPad. If the Spider or the wireless router doesn‘t have DHCP server enabled,
use can either enable it or use static IP address on the iPad.
When iPad has the Wi-Fi enabled, the list of available network will be shown with
SSID. Tap the wireless Spider‘s SSID or the wireless router with wired Spider
connected, the connection between the iPad and the Spider will be automatically
established.
Unless very necessary, DHCP address is highly recommended to avoid
encountering network issue.
License Key
The iPad must load a license key corresponding to the serial number of the Spider
in order to connect to it. License Keys are loaded either directly from the Crystal
Instruments servers or from local disks. While loading license keys, the iPad must
have internet access and the user must have the account password associated with
the Spider‘s serial number.
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License keys are managed through the License Key Management window. All the
loaded license keys are listed here, and a new key can be loaded by entering the
serial number and password and pressing Add License Key.
For the system with more than one license key, only one license key can be set as
active. Only the device associated with the active license key can be controlled by
iPad. To select the active license key, tap on the serial number in the list and then
tap on Set as Active License .
Figure 235: Start Page
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Figure 236: License Key Management
Figure 237:License Key Information
Simulation Mode
The EDM App includes a Simulation Mode that allows the features to be
demonstrated without connecting to an actual front-end device. Just tap Use
Simulation Mode to enter simulation mode as shown in License Key Management
page, or tap Run Simulation Mode as shown in Start Page. Add a license key with
the Serial Number and Password both set to ‗000000‘. Make sure this license is set
on active. When a test is run with this license, demo data will be displayed in the
plot area.
Front-End Detection
Once the iPad and Spider are powered on and connected to the same network, the
iPad will automatically detect the Spider. Press the front-end selection button to
open a list of all detected modules. Front-End detected and connectable are
modules that are ready to be connected to from the iPad. Front-End already
connected by other EDM shows detected modules that are connected to other
devices (like EDM on a computer). They must be disconnected first before the iPad
can connect to them.
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Figure 238. Detected devices
After selecting the Front-End module in the detected list, the selection will be
shown on the control panel. When a device is selected, click the Connect button to
connect to the device.
If the device the iPad is trying to connect to is already running in Black-Box mode, a
warning will be displayed as shown. This warning will appear if the Start button on
the front of the Spider is pressed before connecting from the iPad, or, if a test is
started from the iPad, the iPad is disconnected, and then later reconnected while
that test is still running.
Figure 239. Test status and operations
Create A New Test
If there are existed tests uploaded to the Spider from black-box mode, the list of
tests will be displayed in the test list. Users just need to select a test to run. For
those tests uploaded from black-box mode, the details are illustrated in Black-box
Mode chapter.
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Figure 240. Create a test from iPad
Tap the Create New Test button to create a new test; select the test type from FFT
Analysis, Random, Swept Sine, and Classic Shock; tap the test name to rename it.
Test can also be deleted by tapping the Delete Test button.
Input Channels
Tap the Configure button at the top of the Control Panel to configure the channel
table.
In FFT test, the Input Channels setup include the following items.
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Figure 241. Input channels for FFT test
Sensitivity sets the proportionality factor for the measurement (millivolts per
engineering unit) given as a parameter of the sensor.
Input mode is the electrical interface mode of the sensor. The available options
are DC-Differential, DC-Single End, AC-Differential, AC-Single End, and IEPE.
High-Pass Filter Fc (Hz) sets the digital high-pass filter frequency, used to block
spurious low frequency and DC signals. To measure very low frequency or DC
signals set this value to zero and use the DC-SE or the DC-DI input mode.
In VCS test, the Input Channels setup includes all items which are available in DSA
and the Channel Type which could be the control channel or the monitor channel.
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Figure 242. Input channels for VCS test
Pre-test Status
Some types of test begin with a pre-test. When a pre-test is running, the Pause/Cont.
button will be not available until the pre-test is done.
Figure 243. Control panel of a random test
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Advanced Control Items
The control menu contains manual control options specific to the type of test being
run. For example, there are items to increase or decrease the current test level and
to run in open-loop.
Figure 244. VCS control buttons
Viewing Data
Use the Signals button to choose which signals to display. By default in VCS tests,
the Control Composite view is displayed. This shows the control signal, test profile,
and alarm and abort lines. All other live signals from the test are also available for
display. Signals with the same type and unit can be simultaneously selected and
displayed.
Figure 245. Menu bar
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Figure 246. Signal display setup
The color of the signal lines can be changed.
Figure 247. Signal color setup
A cursor can be added by pressing the add cursor button. Move the cursor by
dragging it across the screen.
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Figure 248. Moving the legend in the composite window
The legend can be moved by tapping and dragging it to anywhere on the screen.
Figure 249. Lengend
The auto-zoom button will zoom out the display to show the best view of the
displayed signal. The display can also be manually zoomed by using two fingers
pinching to zoom in, and the opposite movement to zoom out. Use one finger to
move around the display area.
Axis and signal unit options can be changed in the display format menu. The
horizontal can be viewed with a linear or log scale. The vertical axis can be viewed
with a linear, log, or dB scale. For frequency signals, the units can be changed under
Spectrum Type.
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Figure 250. Signal display setup
Sharing Data
The share menu is used to export the current signal view.
Figure 251. Data sharing menu
Copy Image will save a snapshot of the display to the clipboard.
Save to Photo Library will save the image to the Photo Library on the iPad.
Email will open the Mail App with the image attached.
Print will print the image using an AirPrint compatible printer (consult the Apple
documentation on using printers with the iPad).
Generate Report, Save Test, and Save Signal
The Data Management menu contains features of generating report, saving tests,
and saving signals. Tap Generate report button to create a report in PDF format
containing all testparameters, input channels status, run schedule, test profile,
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shaker parameters, and hardware information.Tap Save test button to save current
test. Tap Save signals to save checked signals which are defined under the Signals
menu.
Figure 252. Data management setup
Here is an example of a test report in PDF format. User can swipe up to view more
parameters in this report.
Figure 253. Sample test report in PDF format
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The report can be saved to iCloud or iPad in PDF format. Or it can be used for an
instant overview and be discarded.
Figure 254. Save functions
To open the saved report, tap the View history or View iCloud button to select the
PDF file with a check mark.
Figure 255. Save and view
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Figure 256. Sample of saved files
Tap the Operation button to view, email, print, save to the other location, and delete
the select PDF files.
Figure 257. View, send, and delete functions
All saved test and signals files can be open by other iPad device, and the PDF files
can be viewed on both iPad and other compatible device such as PC.
Settings
The Settings tab includesEngineering Unit, Plot Setting, andEmail Settings.
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Figure 258. Settings page
Engineering Unit Setting
Figure 259. Changing engineering units
Update Firmware Version
Firmware refers to the DSP software resident on the Spider hardware. The
firmware is stored on the flash memory on board. It can be updated by using either
the EDM App software running on iOS, or the EDM PC software.
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The Update Firmware function can be found under ConfigureTest. By tapping the
Update Firmware button, the current firmware version and the latest available
firmware version will be display. When the current version is older than the
available latest version, tap Download & Update to update the firmware to the latest
version. It is highly recommended to always to the latest firmware to run a test.
Figure 260. Update firmware page
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Real-Time FFT Analysis
FFT analysis is conducted in the DSA real-time operation mode. These applications
involve Digital Signal Processing calculations such as the Auto-Power Spectrum,
Cross Power Spectrum, and Fourier Transform etc. for input channel signals.
Dynamic Signal Analyzer Basics
This section will give an overview of the theory behind the functions performed in
the FFT analysis mode of the Spider module. For more detailed information on this
topic please refer to ―Dynamic Signal Analyzer Basics‖ published by Crystal
Instruments.
The Fourier Transform is one of the most fundamental and popular methods of
signal analysis. It transforms an infinite time waveform into its frequency
components. These frequencies may then be analyzed or further manipulated to
calculate phase or transfer functions. Because the Fourier Transform involves an
infinite sum the signal must be broken into finite blocks of N samples. Each block is
then transformed using the Discrete Fourier Transform (DFT) However, computing
DFT is computationally intensive and so a more efficient algorithm called Fast
Fourier Transform (FFT) was developed.
Some applications of the FFT are listed below:
Power Spectrum
The magnitude of the frequency components of signals are collectively called the
amplitude spectrum. In many applications, the quantity of interest is the power or
the rate of energy transfer that is proportional to the squared magnitude of the
frequency components. The average squared magnitudes of all of the DFT
frequency lines are collectively referred to as the Power Spectrum, Gxx. The
averaging process is more properly termed an ensemble average, wherein the
squared amplitude from N signal blocks at a each measured frequency, f, are
averaged together. Letting an asterisk (*) denote conjugation of a complex number,
the ―power‖ averaging process is defined by:
𝑮𝒙𝒙 𝒇 = 𝑿 𝒇
𝟐
𝟏
𝑵
𝑵
𝑿𝒌 𝒇 𝑿∗𝒌 𝒇
𝒌=𝟏
Cross Spectrum
The Cross Spectrum characterizes the relationship between two spectra. For two
signals 𝑥 and 𝑦, with frequency components X(f)and Y(f)it is defined as:
𝑮𝒙𝒚
296
𝟏
𝒇 =
𝑵
𝑵
𝒀𝒌 𝒇 𝑿∗𝒌 𝒇
𝒌=𝟏
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The Cross Spectrum reflect the correlation between the two signals. While the
Power Spectrum is real-valued, the Cross Spectrum is complex. This means that it
also describes the phase relationship between the two signals.
Frequency Response Function
An important application of Dynamic Signal Analysis is characterizing the inputoutput behavior of physical systems. In linear systems, the output can be predicted
from a known input if the Frequency Response Function (FRF) of the system is
known. The Frequency Response Function, H(f), relates the Fourier Transform of
the input X(f) to the Fourier Transform of the output Y(f) by the simple equation:
𝒀 𝒇 = 𝑯𝒙𝒚 𝒇 𝑿 𝒇
Multiplying both sides of this equation by the conjugate of the input spectrum and
ensemble averaging explains the importance of the power and cross power spectra
as they allow H(f) to be measured and calculated.
𝟏
𝑵
𝑵
𝒀𝒌 𝒇
𝑿∗𝒌
𝒇 = 𝑮𝒙𝒚 𝒇 = 𝑯𝒙𝒚
𝒌=𝟏
𝟏
𝒇
𝑵
𝑵
𝑿𝒌 𝒇 𝑿∗𝒌 𝒇 = 𝑯𝒙𝒚 𝒇 𝑮𝒙𝒙 𝒇
𝒌=𝟏
That is:
𝑯𝒙𝒚 𝒇 =
𝑮𝒙𝒚 𝒇
𝑮𝒙𝒙 𝒇
The fact that Y(f) is dependent on the input X(f) is what makes the system linear.
When measuring the input-output behavior of a system, there is always noise
present that obscures the output. An important measure is how much of the output
is actually caused by the input and a linear process. This is indicated by another
important real-valued spectrum called the (ordinary) Coherence Function. This
coherence function is also defined in terms of the cross spectrum and the power
spectra. Specifically:
𝜸𝟐𝒙𝒚
𝑮𝒙𝒚 𝒇 𝑮∗𝒙𝒚 𝒇
𝒇 =
𝑮𝒙𝒙 𝒇 𝑮𝒚𝒚 𝒇
Note that the coherence can also be stated as the product of an FRF with its inverse
function. That is, if Hxymeasures a process going from input, x, to output, y, Hyx
characterizes the same process, but treats y as the input and x as the output.
𝜸𝟐𝒙𝒚
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𝒇 = 𝑯𝒙𝒚 𝒇
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𝑮∗𝒙𝒚
𝑮𝒚𝒚
=𝑯𝒙𝒚
𝒇 𝑯𝒚𝒙 𝒇
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This product definition indicates the coherence represents an ―energy round trip‖
or a reflection through the process. We apply Gxx to Hxy and get Gxy at the output.
Then we conjugate Gxy (to flip it or reflect x(t) in time) and pass it through Hyx. In a
perfect world, this would result in exactly Gxx as the output of Hyx.
If the system is linear and none of our measurements are contaminated by noise,
the trip is perfect and we get back everything we put in. That is, the coherence will
be exactly 1.0. If the system is non-linear or if extraneous noise has been interjected,
the round-trip will be less efficient and the coherence will be less than one (but
never more).
Thus, the coherence is always between 0 and 1. A coherence of 1.0 means the output
is perfectly explained by the input (i.e. the system is linear). A coherence of 0 means
the output and input are unrelated. Values in-between state the fraction of
measured output power explained by the measured input power and a linear
process. Experienced analysts always use the coherence measurement to quantify
the quality of an FRF measurement at every frequency.
Shock Response Spectrum
The Shock Response Spectrum (SRS) is an entirely different type of spectral
measurement. It is used access the damage potential of a transient event such as a
package drop or an earthquake. The SRS was first proposed by Dr. Maurice Biot in
1932. The SRS is not the spectrum of the pulse. (The FFT provides this.) The SRS is
not a linear operator as the FFT is. That is, an SRS does not uniquely define a single
waveform. Many very different transient time-histories can produce the same SRS.
What the Shock Response Spectrum is, is the representative response of a class of
simple structures to the given transient acceleration time-history. This response is
provided by simulating a group of spring-mass-damper systems sitting on a
common rigid base that is forced to move with the measured acceleration of the
subject shock pulse. Each single degree-of-freedom (SDOF) spring-mass-damper
has a different natural frequency; they all have the same damping factor. The
spectrum is formed by plotting the extreme motion (acceleration) experienced by
each mass against its resonance frequency.
The frequency spacing of the resonance frequencies is logarithmic, much like the
1/3 octave filters used in acoustical analysis. That is, it is a type of proportional
bandwidth analysis where the half-power bandwidth of each SDOF system
increases in proportion to its resonance frequency. The resolution of an SRS is
defined by the number of simulated SDOFs included in the desired analysis span.
The percent damping of all the SDOFs is selectable (although most tests specify 5%
damping).
The extreme motion of each mathematically simulated SDOF mass is monitored by
several peak detectors. The extreme positive and negative accelerations are retained
during the duration of the input pulse and after it. Maximum and minimum values
captured during the pulse‘s duration are termed Primary extremes. Those found
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after the pulse has returned to zero are termed Residual extremes. Specific tests will
prescribe whether positive, negative or extreme absolute values captured should be
displayed. They will further specify Primary, Residual or combined (maxi-max)
data be plotted.
FFT Test Parameters
In the Test Configuration window, the Test Parameters section has settings for the
main analysis parameters of the FFT test.
Figure 261. Test parameters of a FFT test
Frequency Range is defined as the maximum frequency range for the FFT
analysis. Frequency range determines the sampling rate required.
Block Size/ Line are the number of samples in each time blocks and the number
of (un-aliased) spectral lines in each resulting spectrum. Increasing the block size
increases the resolution of the frequency transform and allows lower frequencies to
be detected but it also increases the calculation time and slows down response. The
ratio between Lines and Block Size is determined by the characteristics of A/D
converter and its anti-aliasing filter. In general, this ratio is about 0.46, meaning
that 1024 samples in the waveform will produce about 0.46 * 1024 = 471 lines in the
spectrum.
Window lets the user choose the window to be applied during FFT operation.
Windowing functions can help reduce leakage and increase the precision of the
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frequency measurement. In general select None for triggered transients, Hanning
for general continuous signals and Flat Top when studying tonal data (such as a
rotating machine) and needing extreme accuracy of spectral peaks. Detailed
descriptions about window types and average modes can be found in the DSA
Basics document.
Overlap Ratio sets the proportion of the samples in a time block that are
overlapped (redundant with samples in a prior block) when calculating the FFT of
(un-triggered) continuous signals. Higher overlap ratios result in faster variance
reduction per unit time producing smoother data but they increase the processing
requirements. The Overlap Ratio options are: no overlap, 25%, 50%, 75% and As
High As Possible. For most applications employing a symmetrically tapered
window function (such as Hanning), an overlap of 50% proves optimal.
Average Mode gives options such as Exponential, Linear, and Peak Hold as the
methods used to average the signal spectrum.
AverageNumberis the number of blocks that are averaged for the signal
spectrum. Increasing the average number will reduce the variance of the signal
spectrum.
Measured Signals in FFT
Tap the Signal button to display measured signals in the sine test.
Figure 262. Measured signals setup
Ch1~Ch8 are the native time streams of the input channels.
Block(Ch1)~Block(Ch8) arethe block signals of the input channels.
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APS(Ch1)~APS(Ch8)isthe auto power spectra signalsof the input channels.
Run the Test
When a test is created or selected, tap the green Run button the start running the
test; tap Stop button to stop running the test; tap Pause/Cont. button to
pause/continue the test.
Figure 263. Choose a test to run
The Control Panel is used to start, stop, or pause the test, and shows status
information like test level and elapsed time. The three function buttons in the Test
Operation aear are always available for each type of the test.
Figure 264. Test operations
However the Runtime Status varies among each type of the test. Tap the More> to
display the completed list of status parameters for the FFT test.Test state
information is displayed in the following fields:
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Figure 265. Choose status displayed
Frequency Rangeis defined as the maximum frequency range for the FFT
analysis. Frequency range determines the sampling rate required.
Block Size/ Lines are the size of the time blocks, in number of samples, which the
FFT algorithm transforms to the number of Lines in the frequency domain. Lines
are the useful number of spectral lines. Increasing the block size increases the
resolution of the frequency transform, and allows lower frequencies to be detected,
but increases the calculation time and slows down response.
The ratio between Lines and Block Size is determined by the characteristics of A/D
converter and anti-aliasing filter. In general, the ratio is about 0.46. It means that
given an FFT transform size of 1024, the useful frequency lines is about 0.46 * 1024
= 471.
Sampling Rate Format is just a display preference for sampling rate and allowed
frequency range for user.
Average Mode gives options such as Exponential, linear and peak hold as the
methods used to average the signal spectrum.
AverageNumberis the number of blocks that are averaged for the signal
spectrum. Increasing the average number will reduce the variance of the signal
spectrum.
Frame # is the total number of frame elapsed.
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Total Elapsed is the time elapsed since the test was started.
Output Peak is not controlled by the test. Users can configure the output channels
manually.
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Random Control Tests
In a random control test, the shaker is driven by a wide band random signal.
Feedback control adjusts this drive signal to generate a response that conforms to a
specified test profile. The control algorithm calculates the inverse transfer function
between the output drive and the input control channels, which is the composite of
the amplifier, shaker, and UUT response. The product of the inverse transfer
function and the response profile then gives the output drive spectrum. A phase
randomizer and inverse FFT then generate the random drive output time stream.
The test profile is set under the Broadband Profile and Line Limits section of the
Test Configuration window. The input channels used for control are selected in the
Input Channels settings, and the other channels may be used to monitor responses
of other parts of the test unit. If more than one channel is selected as a control
channel, the channels will be combined, in an average, maximum, or minimum
strategy, to form a composite control signal. The FFT of this signal is the control(f)
signal. The controller monitors the deviation of control(f)from the target profile and
updates the output drive signal in real-time.
The Random Control Process
Random excitation is often used to simulate real world vibration. The purpose of
the random vibration control system is to generate a true random drive signal such
that, when the signal is applied via an amplifier/shaker to the device under test, the
resulting shaker output spectrum will match the user-specified test profile. This
reference profile is defined in the frequency domain in units of
(Acceleration)2/Hz.This signal is to be applied to the UUT for a specified amount of
time to verify the device's ability to function in its service environment.
If the series of components being controlled (i.e., the amplifier, shaker, and testing
structure) is assumed to be an integrated linear system, then it can be described by
a system transfer function H(f) in frequency domain.The frequency spectra of the
control and drive signals, Y(f) and X(f), can be linked together by H(f) as:
Y(f) = H(f) X(f)
Or
X(f) = H(f) -1 Y(f)
where H(f)-1 is called the inverse transfer function.
If a flat spectrum drive signal excites a shaker/test-article system, the resulting
acceleration response spectrum will not be flat.The armature resonances and the
dynamics of the test-article react on the system to produce peaks (resonances) and
valleys (anti-resonances) in the resultant spectrum.
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To apply a specified spectrum to the test article, the drive spectrum must be altered
to correct for the dynamics of the shaker/load combination.This process is
generally referred to as ―Equalization‖.The inverse transfer function is calculated
continuously while the test is running to monitor any change in the system
characteristics. Corrections are applied in real-time.
Given a desired spectrum R(f) (reference spectrum, or profile), the required value
for the drive can be calculated as:
X(f) = H(f) -1 R(f)
where X(f) is the spectrum of the required drive signal.
Once the drive spectrum X(f) is known, there are several ways to generate a random
output signal in the time domain. This signal must have the following properties:
 A spectral shape defined by X(f).
 Free of discontinuities
 A Gaussian amplitude distribution
The algorithm involves these steps:
1. Digitize the input signals and transform them into frequency domain
using the FFT process.
2. Estimate the inverse system transfer function between the averaged
input and output via cross-spectral method.
3. Generate a reference spectrum with random phase.
4. Multiply the reference spectrum by the inverse transfer function, and
apply an Inverse FFT to the result to generate the output-time
waveform.
5. Output the time waveform through a D/A converter.
All these calculations are completed within the period of one time frame to ensure a
very fast control loop time.
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one channel output (drive sig nal)
8 channel inputs (control sig nals)
y2(t)
Output
y1(t)
window
window
window
FFT
FFT
FFT
y2(f)
y1(f)
x(f)
Auto Power
Spectrum
Cross Power
Spectrum
x(t)
Auto Power
Spectrum
channel averaging
Average
Control PSD
Average
Cross PSD
Average
Drive
PSD
Phase
Randomizer
IFFT
Multiply
Compute Inverse
Transfer Function
H-1
Safety Limit Checking
R(f)
Reference
Editor
Figure 266. Random control process flowchart
Control Dynamic Range in Random
One of the key requirements for a random controller is to achieve high control
dynamic range. Control dynamic range is a measure to compare the highest and
lowest spectrum amplitude in the control signal. Spiders can achieve at least 90dB
control dynamic range. This can be measured by a modified Chinese testing
standard, JJG-948. The JJG-948 only requires a control dynamic range up to 60dB.
By modifying the noise floor to lower quantity we can show much higher control
dynamic range.
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Figure 267. Control Dynamic Range in Random
Figure 268. Control Dynamic Range in Random
Safety Features
During the Random test, various safety checks are applied to ensure that the test is
being performed as defined, the shaker response remains measureable, and that the
drive signal remains within certain limits. There are 5 different types of checks that
are performed and an event is triggered if any of the checks fail. The response
actions to these events can be customized under the Event-Action Rules. The 5
checks are,
1. The broadband profile line limits
2. Maximum shaker drive voltage limiting
3. Channel overload or loss detection
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4. RMS limits
5. Limit channels.
The test profile sets limits for the spectral lines of the control signal. If the control
profile falls outside these limits, alarm or abort events will be triggered.
As another safety feature, the hardware detects when input channels are overloaded
or lost, which can indicate a sensor fault or an accidental disconnect, and will abort
the test.
RMS limits and limit channels are described in their own sections below.
In the event of an accidental network disconnection or power loss, the hardware is
able to save test data and state information to non-volatile memory to protect
against loss. For a network disconnection, the test can continue to run in Black Box
mode or save all data and execute an orderly shutdown.
RMS Limits
The overall RMS level of the control channel (or control channels) is monitored and
an alarm or abort event is triggered if it falls outside of predefined limits. These
limits are set under the RMS Limits section of the Test Configuration window.
The table at the top gives the expected RMS and peak values for the current
broadband profile, the peak safety limits of the shaker, and the proportion of the
profile values to the shaker limits as a percentage. This data comes from the given
profile settings and the shaker parameters and cannot be changed here. Just like in
setting the broadband profile, EDM has RMS limits for high- and low-alarm and
high- and low- abort. These events trigger their associated actions defined in the
Event Action Rules. The values are calculated automatically, but can be entered
manually as an absolute magnitude or as a percent change relative to the profile
RMS.
Limit Channels
Any input channels can be set as limit channels. These channels are given limiting
spectral profiles (separate from the test profile), and if the spectrum of these
channels exceeds their profile, an event is triggered. These limit channels can be set
as either Aborting or Notching. Abort limit channels will abort the test when the
response exceeds the limit. Notch limiting channels will lower the output until the
response falls under the limit. These options are set under Test Configuration.
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Figure 269. Limit channel setup on the EDM
To enable a limiting channel, first enable the channel in the Test Configuration>Limit Channel tab, and then click Edit to select either Notching Limit or
Abort Limit or Alarm Limit in the State column here. Click Edit to bring up the
limit profile editor. Click Insert or Append to add lines to the profile.
The picture below shows how the control signal and one of the APS signal will
change after notching is applied. The control signal will drop down in the frequency
ranges where drive signal is lowered.
NOTE: dB value in Limit Profile has the different reference than the dB value in
Signal Display.
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Figure 270. Signal change after notching
Averaging and DOF
In Random mode, an estimate of the spectral values of the input control signal is
generated by averaging the spectral transforms of multiple blocks. These blocks
may be overlapped, where a specified proportion of samples are reused in
subsequent blocks. A windowing function is applied to these blocks before they are
transformed into the spectral domain by the FFT algorithm. A number of these
blocks, set by the average number, are averaged together to create the spectral
estimate. It is this estimate that the control algorithm uses in its calculation of the
system transfer function.
Given a stationary system, it is desirable that this spectral estimate does not vary
significantly from the true power spectral density of the underlying Gaussian
process. Given an infinite average number, this estimate would indeed converge to
the true PSD with zero variance. Unfortunately, such an average number would
make the control loop time prohibitively large.
The spectral estimate varies along a chi-squared distribution with a Degrees-ofFreedom parameter given as a function of average number, block size, and window
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type. As the DOF increases, the variance of this distribution decreases. The
relationship is:
𝐷𝑂𝐹 = 2
𝐸 2 [𝑃 𝑓𝑛 ]
𝑉𝑎𝑟[𝑃 𝑓𝑛 ]
where𝑃 𝑓𝑛 is the spectral estimate, E[] is the expected value, and Var[] is the
variance.
On the basis of control accuracy, it is therefore desirable to increase the DOF as
much as possible (by using a large average number). On the basis of response time,
however, a large average number is undesirable. There is a tradeoff between
accuracy and responsiveness.
Block overlapping can help decrease response time while maintaining a large DOF.
Overlapping involves reusing a specified number of samples in subsequent blocks.
With no overlapping, DOF is approximately twice the average number. With a nonrectangular window, the DOF will be about 1.3 times the average number with 50%
overlap, which will allow a higher DOF value for the same total number of samples.
Increasing overlap beyond 50%, however, will not yield any more advantage in
reducing the variance. However a higher overlap ratio will still be beneficial to
reduce the loop-time of control.
Random Test Parameters
In the Test Configuration window, the Test Parameters section has settings for the
main analysis parameters of the random test.
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Figure 271 .Test parameters for a random test
Lines are the useful number of spectral lines. Increasing the block size increases
the resolution of the frequency transform, and allows lower frequencies to be
detected, but increases the calculation time and slows down response.
The ratio between Lines and Block Size is determined by the characteristics of A/D
converter and anti-aliasing filter. In general, the ratio is about 0.46. It means that given
an FFT transform size of 1024, the useful frequency lines is about 0.46 * 1024 = 471.
Overlap Ratio sets the proportion of the samples in the time blocks that are
overlapped when calculating the FFT. Higher overlap ratios result in faster
response time but increase processing requirements. Overlap ratio, average number
and DOF are dependent to each other.
Overlap ratio can be chosen from no overlap, 50%, 75% and 87.5%. Overlapping greatly
decreases the loop time of the random controller. In older controllers, a 200 line/2000
Hz test can have up to a 100 ms loop time. In the CI controllers, the loop time can be
reduced to as little as 12.5 ms at the same line and Frequency Range.
DOF is the statistical Degrees of Freedom of the spectral averaging. It is a function of
average number, data window and overlap ratio (see above).
Drive Limit (Volt Pk) limits the absolute maximum voltage output of the drive signal
during the scheduled test. If the drive limit is reached but the control signal still does not
reach its target, the system will show a warning sign, Drive Maximized, on the control
panel. For safety reasons, the output signal will not exceed the Drive Limit.
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Response Level Goal During Pre-Test is the expected level reached when the pretest is finished.
Sigma Clipping limits the peaks of the output voltage distribution. Any output
level greater than this number times the variance of the output will be clipped. A
special algorithm is developed to clip the output signal smoothly so no discontinuity
will be output. Clipping produces non-linear effects that can significantly reduce the
system‘s ability to control sharp resonances. This effect results from energy leaking
across the test frequency range from the ―square-wave‖ shape of the clipped peaks.
The apparent noise floor will rise when a sigma- clipping factor of 4 or less is used.
In addition, signal energy out of the test bandwidth may be generated causing
excitation of out-of-band resonances and poor control of resonances in the control
frequency range under some conditions.
Tips: Sigma Clipping applies to the drive channel of a
controller. Kurtosis control applies to the input control
channel of a controller. Do not get confused between two
different goals.
Sigma Clipping is used to try to maximize the shaker rating.
If the vibration test is far below the maximum force rating
of the shaker system, Sigma-Clipping should not be used.
Setting the sigma-clipping value to 5 or more will disable
the sigma-clipping.
Frequency Range (Fa)(Hz) sets the maximum frequency resolved by the FFT
transform by adjusting the sample rate. Selecting CalculatedBy Profile will set the
sample rate based on the other settings especially the frequency range of profile.
Delta Frequency (Hz) is the spacing of the frequency lines in Hertz, and is a function
of the block size and sample rate.
Run Schedule
The Run Schedule allows the test to be run automatically through a preset routine.
This schedule can include loops and periods of running the test at a specified level
and duration The schedule is activated when the test is started.
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Figure 272. Sample run schedule of a random test
Clicking on the right arrow icon of each entry allows users editing this entry. This
operation can modify the loop times, level percentage, and time duration.
Create New Entry button is used to insert a new entry to the last place before the
End Loop entry.
Delete Entry button shows the deletable entries when it is clicked. The loop entries
cannot be deleted. Swipe the entry to the left to display the red Delete button; click
the Delete button to remove the entry from the Run Schedule.
Reorder Entry button shows the entried eligible to be reordered when it is clicked. Press
and hold the Move icon on the right side of each entry; drag the entry to the desired
place to finish reordering the entry.
Test Profile
The test profile is defined in the Test Profile section of the Test Configuration
window. The window shows a graphical plot of the profile, in log magnitude versus
log frequency axes. The profile is shown as a green line, high and low alarm lines
are shown as yellow lines, and high and low abort lines are red lines. Below the
graphical plot the profile points are shown in a table form. The profile is defined as
a set of breakpoints, with defined frequency and amplitude values, connected by
straight lines.
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Figure 273. Random test profile
The breakpoints can be added and deleted. Each point corresponds with a row on
the table below which can be directly edited by entering frequency and magnitude
values. The table also gives the slope of the lines between the points (in decibels per
octave), and the alarm an abort levels in dB above and below the profile level. The
overall RMS level of the profile is shown on the upper left. This overall level can be
changed by clicking on Scale RMS, which scales the ordinate axis to reach the
specified RMS level.
Measured Signals in Random
Tap the Signal button to display measured signals in the random test.
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Figure 274. Measured signals setup
Time Stream is the native time streams of the input channels labeled as Ch1, Ch2,
and drive.
Time Block isthe block signals of the input channels labeled as Block(Ch1),
Block(Ch2), and control_his(t).
Auto Power Spectra is the auto power spectra signals of the input channels
labeled as APS(Ch1), APS(Ch2), and APS(drive).
HighAlarm(f), LowAlarm(f), HighAbort(f), and LowAbort(f) are the limit
lines of the profile.
control_his(t)is the RMS level history of the control signal.
control(f) is the power spectrum of the control signal. If multiple control channels
are used, the control(f) signal is either weighted-averaged spectra from all control
channels, or the maximum spectrum, on per frequency bin base, among all the
control spectra.
profile(f) is the frequency-domain test profile.
noise(f) is the power spectrum of the system noise, measured in the first part of
the pre-test.
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FRF(Ch2, Ch1)is the transmissibility signal between two channels. It will be
available in both complex and real measurement. Currently Random test has no
limitation in the flexibility of FRF channel selection on the PC level.
H(f) is the frequency response function between the drive output and the control
input signal.
Shaker Parameters
Click on Parametersto edit the information from the shaker specifications. This is
important for the safety of the shaker and testing unit. Once the proper shaker
parameters are entered, use the Check Against Shaker feature to confirm the
correctness and expectations.
Figure 275. Shaker parameters setup
Check Against Shaker
Check against Shaker shows the peak acceleration, velocity, displacement, and force
of the profile and compares the values to the shaker limits.
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Figure 276. Check against shaker page
Run the Test
When a test is created or selected, tap the green Run button the start running the
test; tap Stop button to stop running the test; tap Pause/Cont. button to
pause/continue the test.
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Figure 277. Choose a test to run
The Control Panel is used to start, stop, or pause the test, and shows status
information like test level and elapsed time. The three function buttons in the Test
Operation aear are always available for each type of the test.
Figure 278. Test operations
However the Runtime Status varies among each type of the test. Tap the More> to
display the completed list of status parameters for the Random test.Test state
information is displayed in the following fields:
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Figure 279. Choose status displayed
Ctrl RMS is the RMS level of the input control signal. It is an overall rating of the
control signal.
Target RMS is the target RMS level of the current test stage. This is a function of
the test profile and the current test level percentage. The output is increased until
the Ctrl RMS reaches the Target RMS.
Drive Pk is the peak voltage of the output drive signal. This is shown graphically in
the green bar below, as a proportion of the maximum drive voltage limit (set in Test
Parameters).
Remaining is the remaining time of the test, according to the run schedule.
Full Level Elapsed is the time elapsed running at full (100%) output level.
Total Elapsed is the time elapsed since the test was started.
Vel Pk: This is the estimated peak velocity of the control channel. If there is more
than one control channel, only the velocity peak of the first control channel is
displayed. The displacement signal is computed by integrating the acceleration
signal. The accuracy of this computation may be very low if the signal contains
significant amount of low frequency energy. Therefore this display is only used as a
reference.
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Disp PkPk: This is the estimated peak-peak displacement of the control channel.
If there is more than one control channel, only the peak-peak of the first control
channel is displayed. The displacement signal is computed by double-integrating
the acceleration signal. The accuracy of this computation may be very low if the
signal contains significant amount of low frequency energy. Therefore this display is
only used as a reference.
Level is the current output level, as a percentage of the test profile. This is
displayed graphically in the green bar below this field.
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Swept Sine Control Tests
Whereas a Random test generates many frequencies over the band of interest at
once, a swept sine control test generates only one frequency, and sweeps this
frequency through a pre-set range. Feedback from the control signal is then used to
adjust the output amplitude such that the response amplitude of the UUT matches
a test profile. The test profile is a graph of amplitude (usually defined as peak
acceleration) versus frequency.
RSD, or Resonant Search and Dwell, is an extension of the Swept Sine test.
The Sine Control Process
The swept sine control process consists of generating a sine wave output to excite
the device under test, detectingthe control signal input amplitude, comparing the
detected level with the reference amplitude, and updating the drive signal
amplitude appropriately.
Reference
Control (measured from
test species)

Comparator
Drive (output to the
shaker amplifier)
Figure 280. Sine control process
To measure the level in the incoming control signal, the detector can use a tracking
filter, or can measure the RMS, peak, or mean value of the signal. When using a
tracking filter, amplitude and phase data are produced while the other
measurement methods only produce amplitude data.
If more than one control channel is used, then the output of each detector is
combined in the Channel Averaging Block.
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Chn 1
Detector
Exp.
Averaging
Chn 2
Detector
Exp.
Averaging
Chn 3
Detector
Exp.
Averaging
Averaging
Logic
Channel
Averaging
Block
Control (A,  )
...
Figure 281. Control signal calculation flowchart
Tracking filters greatly reduce the noise and harmonic signals above and below the
sine drive frequency. Their center frequency is always tuned to the current drive
frequency, allowing all other signals to be rejected from measurement and control.
The filter bandwidth can be either fixed or proportional to the current frequency.
A tracking filter with changing bandwidth and center frequency
can eliminate the noise outside the band
f1
f2
frequency
Figure 282. An example of tracking filters
The Spider system continually updates the tracking filter coefficients based on the
current center frequency and bandwidth. It has a stop band rejection of about –60
dB.The output of the filter is averaged to produce a control amplitude value, which
is then used by the comparator to correct the output drive amplitude.
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Figure 283. Tracking filters in EDM
In general, the narrower the bandwidth of the tracking filter, the sharper the
resonance that the control system can calculate. As shown in the picture above, the
red line that uses 7% bandwidth can show sharper resonance than the green line
which uses the 25% bandwidth. However, the bandwidth of the filter also affects the
speed of response time of a control system. The system response time is inversely
proportional to the filter bandwidth. Therefore, choosing the right bandwidth of the
tracking filters is usually a trial process.
Sweeping Frequency
Filter coefficients
f1
calculation
Filter bandwidth type (fixed
or proportional)
frequency
Figure 284. Tracking filter theory
The Peak, Mean, and RMS measurement methods analyze the data in blocks, with a
length determined by the bandwidth settings:
Block length (second) = 1/bandwidth (Hz)
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Both fixed and proportional bandwidths can be used.The block duration is constant
for fixed bandwidth, and changes with the drive frequency when using proportional
bandwidth.
History duration
RMS Detector
Peak Detector
DC Detector
Figure 285. History duration
If N is the length of this block, in samples, then the RMS is defined as
RMS 
N 1
 x( i )
i0
And the Mean is the statistical Mean Absolute Deviation:
Mean 
N 1
 ABS ( x(i ))
i 0
With RMS, Mean, and Peak measurement strategy, signals at harmonics of the
drive frequency can contribute to the final overall measurement result.Therefore,
the drive level may be lower than when a tracking filter is used. In other words,
when tracking filters are turned on, the UUT might get over-tested; when RMS,
Mean and especially Peak are used as measurement strategy, the UUT might get
under-tested.
Note:When the input channels are not well calibrated, the
DC offset in the input will contribute to the calculation
results of Sine amplitude spectrum. This error will
eventually be reflected in the control accuracy. This is not a
big problem for high frequency (say larger than 10Hz) but
for low frequency control, the DC offset will have bad
impact. Therefore, the system should be well calibrated
before they are used.
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Safety Features
In the Sine mode, there are a number of safety features that help prevent damage to
the shaker and related equipment. During a shake test, 5 different types of checks
are performed and an event is triggered if any of these checks fail. The response
actions to these events can be customized under Event-Action Rules. The 5 checks
are 1) the profile line limits, 2) Maximum shaker drive voltage limiting, 3) Channel
overload or loss detection,and 4) Limit channels.
The test profile has lower and upper limits for the control channel over the
frequency range of the test. If the control signal falls outside these limits, alarm or
abort events will be triggered.
The system also detects when input channels are overloaded or lost which can
indicate a sensor fault or an accidental disconnect. The test will be aborted if this
occurs.
Limit channels are described in the next section.
In the event of an accidental network disconnection or power loss, test data is saved
to non-volatile memory to protect against loss. For a network disconnection, the
test can either continue running in Black Box mode or save all data or execute an
orderly shutdown.
Limit Channels
Any input channels can be set as limit channels. These channels are given limiting
spectral profiles (separate from the test profile), and if the spectrum of these
channels exceed their profile and event is triggered. These limit channels can be set
as either Aborting or Notching. Abort limit channels will abort the test when the
response exceeds the limit. Notch limiting channels will lower the output until the
response falls under the limit. These options are set under Input Channel Setup.
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Figure 286. Limit channels setup on the EDM for a sine test
To enable a limiting channel, first set the channel type to Limit in the Channel
Setup tab, and then select either Notching Limit or Abort Limit in the State
column here. Click Edit to bring up the limit profile editor. Click Insert or
Append to add lines to the profile.
Sine Test Parameters
In sine mode, this section of the Test Configuration window is used to configure
settings related to the Sine mode analysis parameters.
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Figure 287. Sine test parameters
Maximum Drive (Volts) is the maximum RMS voltage output for the initial test level.
Drive Limit (Volt Pk) limits the absolute maximum voltage output of the drive signal.
If the drive limit is reached before the control signal reaches its target, the system will
show a Drive Maximized warning. The output signal will not exceed the Drive Limit.
Sweep Type: Linear or Logarithmic. When the Sweep Type is Linear, the Sweeping
Speed is in the unit of Hz/Min; When the Sweep Type is Logarithmic, the Sweep Speed
can be defined in unit of Octave/Min or Decade/Min.
Measurement Strategy defines how the sine waves are measured. The selections are:
Proportional Filter, Fixed Filter, RMS, Mean and Peak. In the perfect world
when the sine signals have no distortion, all the measurement strategies will generate the
same results. When signals are distorted, the controller will generate different drive
magnitude by selecting different Measurement Strategy.
Run Schedule
A sine test is controlled by a run schedule. The schedule contains one or more
entries that define test stages. A stage defines the output behavior and timing The
Run Schedule sets the sequence of test stages that are activated when the test is run.
A test stage is either a sweep entry, a step sine entry, or a fixed dwell entry.
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Figure 288. An example of sine run schedule
Clicking on the right arrow icon of each entry allows users editing this entry. This
operation can modify all the parameters as shown below.
The sweep entry sweeps the output between a low frequency and high frequency
at a fixed rate or over a fixed period of time. The sweep rate can be logarithmic or
linear, depending on the setting under Test Parameters. The Level sets the
amplitude of the expected control signal, relative to the reference profile, and the
Sweep# sets the number of times the sweep will be repeated.
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Figure 289. Sweep sine entry parameters setup
A step sine entry steps the output from the low frequency to the high frequency at
increments given by DeltaF(Hz). The duration at each step can be either set
system-wide, given as a time period, or given as number of cycles.
Figure 290. Step sine entry parameters setup
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A fixed dwell entry holds the output at a fixed frequency for a given duration.
There is also an option to dwell at frequencies given in the dwell list.
Figure 291. Fixed dwell entry parameters setup
Users can create three types of entry by clicking corresponding Create Entry
buttons.
Delete Entry button shows the deletable entries when it is clicked. Swipe the entry
to the left to display the red Delete button; click the Delete button to remove the
entry from the Run Schedule.
Reorder Entry button shows the entried eligible to be reordered when it is clicked. Press
and hold the Move icon on the right side of each entry; drag the entry to the desired
place to finish reordering the entry.
Test Profile
The graph below shows the profile shape, along with four other lines: the Low- and
High-Alarm Levels and the Low-High- Abort levels. The profile consists of
breakpoints at a given frequency and magnitude connected by line segments. The
breakpoints can be added, deleted, and manually dragged around the graph. Each
point corresponds with a row on the table under the Profile Table tab. This table
can be directly edited by entering frequency and magnitude values in the cells. The
magnitudes are listed as acceleration, velocity, and displacement.
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Figure 292. Sine test profile
There are three types of segments that can connect the breakpoints: constant
amplitude, log-log slope, and linear slope. The segment type can be edited by
clicking the Edit A/V/D button at the bottom of the Test Profile page.
Figure 293. Segment type setup
During the full test, if the response magnitude falls outside of the Alarm or Abort lines
for longer than the Abort Latency value, then an Alarm or Abort event will be triggered.
Measured Signals in Sine
Tap the Signal button to display measured signals in the sine test.
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Figure 294. Measured signals setup
Time Stream is the native time streams of the input channels labeled as Ch1, Ch2,
and drive.
Time Block isthe block signals of the input channels labeled as Block(Ch1),
Block(Ch2), control_his(t), and frequency_his(t).
Spectrumis the sine measurement value plotted across the frequency. Usually it is
represented in acceleration peak value. The sine measurement is taken at the
output of tracking filter. In Sine the Spectrum in Sine is not a snapshot of a
measurement. It is just the history trace drawn across the whole frequency. The
resolution of Spectrum signal has nothing to do with the resolution of frequency
change in the control process.Those spectrum signals are labeled as Spectrum(Ch1),
Spectrum(Ch2), and Spectrum(drive).
HighAlarm(f), LowAlarm(f), HighAbort(f), and LowAbort(f) are the limit
lines of the profile.
control_his(t)is the RMS level history of the control signal.
frequency_his(t) is the time trace of the frequency.
control(f) is the power spectrum of the control signal. If multiple control channels
are used, the control(f) signal is either weighted-averaged spectra from all control
channels, or the maximum spectrum, on per frequency bin base, among all the
control spectra.
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profile(f) is the frequency-domain test profile.
FRF(Ch2, Ch1)is the transmissibility signal between two channels. It will be
available in both complex and real measurement. Currently Random test has no
limitation in the flexibility of FRF channel selection on the PC level.
H(f) is the frequency response function between the drive output and the control
input signal.
Shaker Parameters
Click on Parametersto edit the information from the shaker specifications. This is
important for the safety of the shaker and testing unit. Once the proper shaker
parameters are entered, use the Check Against Shaker feature to confirm the
correctness and expectations.
Figure 295. Shaker parameters setup
Check Against Shaker
Check against Shaker shows the peak acceleration, velocity, displacement, and force of
the profile and compares the values to the shaker limits.
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Figure 296. Check against shaker page
Run the Test
When a test is created or selected, tap the green Run button the start running the
test; tap Stop button to stop running the test; tap Pause/Cont. button to
pause/continue the test.
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Figure 297. Choose a test to run
The Control Panel is used to start, stop, or pause the test, and shows status
information like test level and elapsed time. The three function buttons in the Test
Operation aear are always available for each type of the test.
Figure 298. Test operations
However the Runtime Status varies among each type of the test. Tap the More> to
display the completed list of status parameters for the Sine test.Test state
information is displayed in the following fields:
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Figure 299. Choose status displayed
Ctrl Peak is the averaged Peak of the input control signals.
Target Peakis the target Peak level of the current test stage. This is a function of
the test profile and the current test level percentage. The output is increased until
the Ctrl Peak reaches the Target Peak.
Drive Peak is the peak voltage of the output drive signal. This is shown graphically
in the green bar below, as a proportion of the maximum drive voltage limit (set in
Test Parameters).
Frequency is the current sweeping frequency.
RemainingTime is the remaining time of the test, according to the run schedule.
Full Level Elapsed is the time elapsed running at full (100%) output level.
Total Elapsed is the time elapsed since the test was started.
Sweep Count is the number of sweep count.
Sweeping Rate is the speed of sweeping.
Vel Pk: This is the estimated peak velocity of the control channel. If there is more
than one control channel, only the velocity peak of the first control channel is
displayed. The velocity signal is computed by integrating the acceleration signal.
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The accuracy of this computation may be very low if the signal contains significant
amount of low frequency energy. Therefore this display is only used as a reference.
Disp PkPk: This is the estimated peak-peak displacement of the control channel.
If there is more than one control channel, only the peak-peak of the first control
channel is displayed. The displacement signal is computed by double-integrating
the acceleration signal. The accuracy of this computation may be very low if the
signal contains significant amount of low frequency energy. Therefore this display is
only used as a reference.
Level is the current output level, as a percentage of the test profile. This is
displayed graphically in the green bar below this field.
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Classic Shock Control Tests
A Shock control test outputs a series of pulses to excite the structure under test. The
response is measured at one or more locations on the structure and a spectral
analysis is used to determine its response and resonance characteristics. This pulse
response is an approximation of the impulse response, which requires a pulse of
infinite amplitude. The Fourier transform of the impulse response is the Frequency
Response Function (FRF) of the system.
The Shock control process is essentially a time-domain waveform replication
process that uses an FFT based algorithm to correct for the test system dynamics.
The algorithm is similar to the one used for Random Control. The difference is in
how the test profile is defined: in random control, it‘s defined in the frequency
domain; while in shock control, it‘s defined in the time domain.
It is assumed that the test system is linear, which means that its response to any
input can be predicted from its Frequency Response function. In the control
process, this FRF is continually estimated and updated, and used to calculate the
output drive signal. This output waveform should cause the test system to respond
in a way that the control signal matches the test profile.
x(t) * h(t)
drive x(t)
y(t)
Shaker/Testing
System
X(f) H(f)
control y(t)
= Y(f)
Figure 300. Mathematics of Control System
The system output y(t) can be calculated as the convolution between the system
input, x(t), and the system impulse response, h(t).
y(t) = h(t) * x(t)
However, convolutions are tricky to calculate, and it may be impossible to fully
determine the impulse response. Fortunately, this convolution is equivalent to a
multiplication in the frequency domain. The system output y(t) is replaced with the
output spectrum Y(f), the input x(t) is replaced with X(f), and the impulse response
h(t) is replaced with the frequency response function H(f). Calculating the Fourier
transforms Y(f) and X(f) are straightforward, and determining H(f) is much easier
than h(f).
The controller calculates the required test system input x(t) by:
x(t) = IFFT( X(f) ) = IFFT( R(f)/H(f) )
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= IFFT( FFT( r(t) ) / H(f) )
whereR(f) is the test profile in the frequency domain and IFFT is the inverse FFT
(an algorithm for the Fourier transform). The test profile is specified by the user as
r(t), in the time domain, and is then transformed into R(f) before the test begins.
In the classic shock test, r(t) can be a half-sine, sawtooth, triangle, rectangle,
trapezoid, or haver-sine shape.
The target pulse shape can be half-sine, sawtooth, triangle, rectangle, trapezoid, or
haver-sine. The pulse itself is always one-sided — its displacement is only in one
direction. A series of these pulses would cause an unbounded armature excursion of
the shaker in one direction, which is not physically possible. To keep the armature
centered, each pulse must have a zero mean displacement. This is done by adding a
compensating pre- and post-tail to the pulse.
Waveform Compensation
At the end of each pulse output, the shaker must return to its rest position. However,
the pulse shapes used in the classical shock test are one-sided, meaning that, if used
by themselves, they would leave the shaker armature with residual displacement
and velocity. A series of these pulses would cause the armature to travel all the way
to its stops, and then no more outputs would be possible.
Compensation is the method of ―correcting‖ the control signal so that the ending
displacement and velocity is always zero. It involves adding smaller pulses before
and after the main pulse.
Acceleration
time
Velocity
time
Displacement
time
Figure 301. A Single Square Pulse and Its Effects on Velocity and
Displacement over Time
Given a main pulse shape, there are different algorithms that can be used to
generate an optimized waveform. Compensation pulses can be added before or
after the main pulse.
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The figure below shows a half-sine pulse that has been properly compensated, along
with its velocity and displacement profile.
Figure 302. Shock Pulse Compensation
When generating the profile waveform, it is important not to exceed the limits of
the shaker. These limits include the voltage and current capabilities of the power
supply driving the system, and the ability of the system to generate peak
acceleration, force, velocity, and displacement levels.
Safety Features
In sine mode, there are a number of safety features that help prevent damage to the
shaker and related equipment. During a shake test, 5 different types of checks are
performed and an event is triggered if any of these checks fail. The response actions
to these events can be customized under Event-Action Rules. The 3 checks are
1. Maximum shaker drive voltage limiting
2. Channel overload or loss detection
3. Shock abort limits.
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The system also detects when input channels are overloaded or lost which can
indicate a sensor fault or an accidental disconnect. The test will be aborted if this
occurs.
In the event of an accidental network disconnection or power loss, the hardware is
able to save test data and state information to non-volatile memory to protect
against loss. For a network disconnection, the test can continue to run in Black Box
mode or save all data and execute an orderly shutdown.
Shock Abort Limit
Shock abort limits are similar to the abort lines in the sine and random tests, but
are defined in the time domain rather than the frequency domain. If the level of the
control signal, within the vicinity of the pulse output, falls outside these limits then
an abort event is triggered.
Figure 303. Shock Abort Limit
The top of the window shows the pulse acceleration shape as a green line with the
beginning of the pulse at time zero. The abort limits are red lines (this is the same
graph as shown in the Shock Settings section).
These limits can be set according to three standards: Mil-Std 810, Mil-Std 202F,
and the ISO mechanical shock test standard. The text fields show the characteristics
of the limits — high and low values as a percentage of the main pulse peak
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amplitude for the left tail, main pulse, and right tail; and the time length of the left
and right tails as a percentage of pulse width. The figure below shows a graphic
definition of these values (this figure can be shown by clicking the button Show
Fig.).
Figure 304. Shock limit definitions
There is also an option to set customized limits, with points entered on the table
below.
Draw main pulse zooms the graph in to show the main pulse outline.
The figures below show some standard waveform shapes and tolerances.
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Figure 305. Standard waveform shapes and tolerances of a shock pulse
Shock Test Parameters
In the shock test, this section of the Test Configuration window is used to configure
settings related to the shock test parameters. The Block Size, Block T, dT, Sampling
Rate, and Frequency Range are automatically calculated and users‘ input is not
required.
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Figure 306. Shock test parameters setup
Average Number is the number of blocks that are averaged for the response
profile. Higher averages will smooth out the response to any transient events. In
general this value should be between 2 and 5.
Drive Limit (Volt Pk) limits the absolute maximum voltage output of the drive
signal. If the drive limit is reached before the control signal reaches its target, the
system will Drive Maximized warning. The output signal will not exceed the Drive
Limit.
Interval Between Pulse is the number of second between adjacent pulses in
time length.
Run Schedule
When a test is run, it executes the entries in the run schedule. These entries define
test stages at certain levels and durations.
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Figure 307. An example of the shock test run schedule
This schedule can also include loops to repeatedly execute a series of entries. When
the test is running, pulses will be continually output at their set interval. The
schedule is activated when the test is started.
Clicking on the right arrow icon of each entry allows users editing this entry. This
operation can modify the loop times, level percentage, and pulse numbers.
Create New Entry button is used to insert a new entry to the last place before the
End Loop entry.
Delete Entry button shows the deletable entries when it is clicked. The loop entries
cannot be deleted. Swipe the entry to the left to display the red Delete button; click
the Delete button to remove the entry from the Run Schedule.
Reorder Entry button shows the entried eligible to be reordered when it is clicked. Press
and hold the Move icon on the right side of each entry; drag the entry to the desired
place to finish reordering the entry.
Test Profile
This is where the pulse shape and time characteristics are set. The graph below
shows the pulse shape as a green line. The pulse is set as an acceleration profile, and
this shape is integrated to draw the velocity and displacement profiles. The
acceleration graph also shows the abort limits as red lines above and below the
pulse.
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Figure 308. Shock test profile
Pulse Type is the shape of the pulse. The options are half-sine, terminal-peak
sawtooth, initial-peak sawtooth, triangle, rectangle, trapezoid, and haver-sine. The
shapes have different frequency characteristics and are suitable for simulated
different impulse conditions. Many testing standards specify the pulse shape to be
used.
Main Pulse Tailsare the compensation tails described below. The time length of
the pre- and post-tails can be set according to these four standards: MIL_STD 810,
MIL_STD 202F, ISO_Standard, and IEC_60068_2_27.
Show A/V/D sets the unit in Acceleration, Velocity, or Displacement.
Amplitude sets the peak acceleration value of the pulse.
Pulse width sets the width of the pulse in milliseconds. Narrower pulses have
greater high-frequency components.
Measured Signals in Shock
Tap the Signal button to display measured signals in the shock test.
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Figure 309. Measured signal setup
Time Stream is the native time streams of the input channels labeled as Ch1, Ch2,
drive(t), profile(stream), and control(stream).
Time Block isthe block signals of the input channels labeled as Block(Ch1),
Block(Ch2), and Block(drive).
HighAlarm(t), LowAlarm(t), HighAbort(t), and LowAbort(t) are the limit
lines of the profile.
drive(t) is the time stream of the drive signal.
control(t)is the control signal time stream.
control_scrollis the RMS level history of the control signal.
error_t is the error between the actual time domain profile and the time domain
control signal of each block.
noise(t) is the time domain system noise, measured in the first part of the pre-test.
profile(f) is the frequency-domain test profile.
drive(f) is thethe frequency domain of the drive signal.
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control(f) is the power spectrum of the control signal. If multiple control channels
are used, the control(f) signal is either weighted-averaged spectra from all control
channels, or the maximum spectrum, on per frequency bin base, among all the
control spectra.
hinv(f) is the frequency response function of the system when inverted pulses are
output.
Shaker Parameters
Click on Parametersto edit the information from the shaker specifications. This is
important for the safety of the shaker and testing unit. Once the proper shaker
parameters are entered, use the Check Against Shaker feature to confirm the
correctness and expectations.
Figure 310. Shaker parameters setup
Check Against Shaker
Check against Shaker shows the peak acceleration, velocity, displacement, and force
of the profile and compares the values to the shaker limits.
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Figure 311. Check against shaker page
Run the Test
When a test is created or selected, tap the green Run button the start running the
test; tap Stop button to stop running the test; tap Pause/Cont. button to
pause/continue the test.
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Figure 312. Choose a test to run
The Control Panel is used to start, stop, or pause the test, and shows status
information like test level and elapsed time. The three function buttons in the Test
Operation aear are always available for each type of the test.
Figure 313. Test operations
However the Runtime Status varies among each type of the test. Tap the More> to
display the completed list of status parameters for the Shock test.Test state
information is displayed in the following fields:
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Figure 314. Choose status displayed
Ctrl Peak is the averaged Peak of the input control signals.
Target Peakis the target Peak level of the current test stage. This is a function of
the test profile and the current test level percentage. The output is increased until
the Ctrl Peak reaches the Target Peak.
Ctrl RMS is the RMS level of the input control signal. It is an overall rating of the
control signal.
Drive Pk is the peak voltage of the output drive signal. This is shown graphically in
the green bar below, as a proportion of the maximum drive voltage limit (set in Test
Parameters).
RemainingPulse is the remaining number of pulse of the test, according to the
run schedule.
Full Level Elapsed is the time elapsed running at full (100%) output level.
Total Elapsed is the time elapsed since the test was started.
Vel Pk: This is the estimated peak velocity of the control channel. If there is more
than one control channel, only the velocity peak of the first control channel is
displayed. The displacement signal is computed by integrating the acceleration
signal. The accuracy of this computation may be very low if the signal contains
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significant amount of low frequency energy. Therefore this display is only used as a
reference.
Disp PkPk: This is the estimated peak-peak displacement of the control channel.
If there is more than one control channel, only the peak-peak of the first control
channel is displayed. The displacement signal is computed by double-integrating
the acceleration signal. The accuracy of this computation may be very low if the
signal contains significant amount of low frequency energy. Therefore this display is
only used as a reference.
Level is the current output level, as a percentage of the test profile. This is
displayed graphically in the green bar below this field.
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Black-box Mode
Introduction
The Spider platform from Crystal Instruments operates as a real-time data
acquisition and analysis system while connected to a desktop PC. It can also
function as a stand-alone data recording system that does not require a separate
computer. This second mode is called Black Box Mode and it is unique to Crystal
Instruments‘ products. A computer is used to set up test parameters and to
download test data after the test has been run. While running, the Spider operates
autonomously according to a pre-set run schedule. Only single module systems can
run in black box mode.
Running in Black Box mode eliminates the reliability issues caused by PCs in realtime control and data acquisition applications.
Black Box mode is ideal for production tests or long-duration tests. It is ideal for
data acquisition applications that run without people in attendance.
Figure 315. A typical connection method
In order to use iPad to control the existing tests on the Spider, those tests must be
uploaded from the desktop version of EDM before using iPad to take control. Every
time a test is run from the desktop EDM, it is automatically uploaded if the option
―Always overwrite‖ is checked. The Spider can also store 7 other test configurations,
for a total of 8.
Note: Currently only Random, Sine, Shock, and FFT tests are supported on the iPad.
Uploading Tests
In order to run a test on the Spider, it must be uploaded from the desktop version of
EDM. Every time a test is run from the desktop EDM, it is automatically uploaded if
the option ―Always overwrite‖ is checked. The Spider can also store 7 other test
configurations, for a total of 8.
To see which tests are currently loaded on the Spider, go to the Setup menu in EDM
and select Black Box Setup (make sure the Spider is turned on and connected
first). From this windows, the loaded tests can be deleted or new tests can be
uploaded (错误！未找到引用源。).
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To upload another test, click on Upload Test. A list of all tests in the current
database is shown. Select the test(s) to upload and press Upload (错误！未找到引
源。).
Figure 316. List of black box test and function buttons
Figure 317. Choose a test to upload to the Spider
Now that the tests are uploaded to the Spider, they are ready to be run in Black Box
Mode.
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To see which tests are currently uploaded on the Spider, go to the Setup menu in
EDM and select Black Box Setup (make sure the Spider is turned on and
connected first). From this window as shown below, the loaded tests can be deleted
or new tests can be uploaded.
To upload another test, click on Upload Test. A list of all tests in the current
database is shown. Select the test(s) to upload and press Upload.
Now that the tests are uploaded to the Spider, they are ready to be run in Black Box
Mode or from the iPad.Open EDM App on the iPad; connect to the front-end; the
list of the test which can be run in the black-box mode is shown as below; select the
test and go back to control panel to tap Run Test button to start the test in the
black-box mode.
Figure 318. Choose a test to run
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Limited Warranty & Limitation of Liability
Each CI product is warranted to be free from defects in material and workmanship
under normal use and service. The warranty period is one year for the Spider
hardware and its accessories. The warranty period begins on the date of shipment.
Parts, product repairs and services are warranted for 90 days. This warranty
extends only to the original buyer or end-user customer of a CI authorized reseller,
and does not apply to fuses, disposable batteries or to any product which, in CI's
opinion, has been misused, altered, neglected or damaged by accident or abnormal
conditions of operation or handling. CI warrants that software will operate
substantially in accordance with its functional specifications for one year and that it
has been properly recorded on non-defective media. CI does not warrant that
software will be error free or operate without interruption.
CI authorized resellers shall extend this warranty on new and unused products to
end user customers only but have no authority to extend a greater or different
warranty on behalf of CI. Warranty support is available if the product is purchased
through a CI authorized sales outlet or the Buyer has paid the applicable
international price. CI reserves the right to invoice the Buyer for importation costs
of repair/replacement parts when product purchased in one country is submitted
for repair in another country.
CI's warranty obligation is limited, at CI's option, to refund of the purchase price,
free of charge repair, or replacement of a defective product which is returned to a CI
authorized service center within the warranty period.
To obtain warranty service, contact your nearest CI authorized service center or
send the product, with a description of the difficulty, postage and insurance prepaid
(FOB Destination), to the nearest CI authorized service center. CI assumes no risk
for damage in transit. Following warranty repair, the product will be returned to
Buyer, transportation prepaid (FOB Destination). If CI determines that the failure
was caused by misuse, alteration, accident or abnormal condition of operation or
handling, CI will provide an estimate of repair costs and obtain authorization before
commencing the work. Following repair, the product will be returned to the Buyer
transportation prepaid and the Buyer will be billed for the repair and return
transportation charges.
This warranty is the buyer's sole and exclusive remedy and is in lieu of
all other warranties, expressed or implied, including but not limited to
any implied warranty of merchantability or fitness for a particular
purpose. CI shall not be liable for any special, indirect, incidental or
consequential damages or losses, including loss of data, whether
arising from breach of warranty or based on contract, tort, reliance or
any other theory.
Since some countries or states do not allow limitation of the term of an implied
warranty, or exclusion or limitation of incidental or consequential damages, the
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limitations and exclusions of this warranty may not apply to every buyer. If any
provision of this Warranty is held invalid or unenforceable by a court of competent
jurisdiction, such holding will not affect the validity or enforceability of any other
provision.
Hereby, Crystal Instruments, declares that this MINI-DYNAMIC SIGNAL ANALYZER AND
DATA RECORDER is In compliance with the essential requirements and other relevant
provisions of Directive 1999/5/EC.
The AC plug considered as disconnect device of power supply.
I/P AC 100-300V, 50/60Hz, 1.5A, O/P 15.0V, 4A
Environment friendly disposal
You can help protect the environment!
Please remember to respect the local
regulations: hand in the non-working electrical
equipments to an appropriate waste disposal
centrer.
0700
FCC Warning:
This device complies with part 15 of the FCC Rules. Operation is subject to the following
two conditions: (1) This device may not cause harmful interference, and (2) this device must
accept any interference received, including interference that may cause undesired operation.
Any Changes or modifications not expressly approved by the party responsible for compliance
could void the user's authority to operate the equipment.
Note: This equipment has been tested and found to comply with the limits for a Class B digital
device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable
protection against harmful interference in a residential installation. This equipment generates uses
and can radiate radio frequency energy and, if not installed and used in accordance with the
instructions, may cause harmful interference to radio communications. However, there is no guarantee
that interference will not occur in a particular installation. If this equipment does cause harmful
interference to radio or television reception, which can be determined by turning the equipment off
and on, the user is encouraged to try to correct the interference by one or more of the following
measures:
-Reorient or relocate the receiving antenna.
-Increase the separation between the equipment and receiver.
-Connect the equipment into an outlet on a circuit different from that to which the receiver is
connected.
-Consult the dealer or an experienced radio/TV technician for help.
To maintain compliance with FCC’s RF exposure guidelines, this equipment should be installed and
operated with a minimum distance of 20cm between the radiator and your body.
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