Aclara Power Line Systems Y72148-1 Frequency Hopping Spread Spectrum Transceiver User Manual RF Application Notes Rev 11
Aclara Power-Line Systems Inc. Frequency Hopping Spread Spectrum Transceiver RF Application Notes Rev 11
Users Manual
RF-TWACS Based AMR System
Application Notes
Revision 1
a product of
Distribution Control Systems, Inc.
Confidential and Proprietary
Copyright 2001- 2003. All Rights Reserved
PROPRIETARY NOTICE
The information contained in this document is private to Distribution Control Systems, Inc., St. Louis, Missouri (DCSI).
This information may not be published, reproduced, or otherwise disseminated without the express written authorization of
DCSI.
Any software or firmware described in this document is furnished under a license and may be used or copied only in
accordance with the terms of such license.
DISCLAIMER
The information in this document is subject to change without notice and should not be construed as a commitment by
DCSI. DCSI assumes no resp onsibility for any errors that may appear in this document.
No responsibility is assumed for the use or reliability of software on equipment that is not supplied by DCSI.
TWACS is a registered trademark of Distribution Control Systems, Inc., St. Louis, MO.
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TABLE OF CONTENTS
1 AUDIENCE............................................................................................................................................................... 1
2 INTRODUCTION..................................................................................................................................................... 1
2.1 BASIC CONCEPTS ..............................................................................................................................................1
2.2 BENEFITS ...........................................................................................................................................................1
2.3 PRINCIPLES OF OPERATION ..............................................................................................................................1
3 SYSTEM NOMENCLATURE................................................................................................................................ 4
4 SYSTEM OVERVIEW ............................................................................................................................................. 8
4.1 GENERAL SYSTEM THEORY OVERVIEW ............................................................................................................8
4.2 RF HARDWARE SPECIFICATIONS, INSTALLATION, OPERATIONS & MAINTENANCE ........................................9
4.2.1 Centron Meter.......................................................................................................................................9
4.2.1.1 Initial Installation and Change-outs .........................................................................................11
4.2.2 Remote Meter (gas/water) Transceiver (RMTR)........................................................................11
4.2.2.1 RMTR Specifications ....................................................................................................................11
4.2.2.2 Initial Installation and Change-outs .........................................................................................12
4.2.2.3 RMTR Operations ..........................................................................................................................12
4.2.2.4 RMTR Maintenance.......................................................................................................................14
4.2.3 Electric Meter Transceiver (EMTR)...............................................................................................14
4.2.3.1 EMTR Specifications ....................................................................................................................14
4.2.3.2 Initial Installation and Change-outs .........................................................................................15
4.2.3.3 EMTR Operations ..........................................................................................................................15
4.2.3.4 EMTR Maintenance.......................................................................................................................16
4.2.4 Hand-Held Transceiver (HHTR) – Verification and Installation Tool ...................................16
4.2.4.1 HHTR Specifications ....................................................................................................................16
4.2.4.2 HHTR Operation.............................................................................................................................17
4.2.4.2.1 RMTR Configuration.....................................................................................................................18
4.2.4.2.2 RMTR Network Insertion...................................................................................................... 18
4.2.4.2.3 EMTR Installation .................................................................................................................. 19
4.2.4.2.4 Site Survey .............................................................................................................................. 19
4.2.4.2.5 Transceiver Equipment Diagnostics................................................................................ 20
4.2.4.2.6 Installation Data Collection................................................................................................. 20
4.2.4.2.7 Other HHTR Applications .................................................................................................... 20
4.2.4.3 HHTR Maintenance .......................................................................................................................20
4.3 RF-TWACS SYSTEM SOFTWARE – CENTRAL COMMUNICATION EQUIPMENT..............................................21
4.3.1 Data Available From Meters............................................................................................................21
4.3.2 CCE Data Requirements..................................................................................................................21
4.3.2.1 Initial Installation ...........................................................................................................................21
4.3.2.2 Change-outs ...................................................................................................................................21
4.3.3 Data Availability .................................................................................................................................21
4.3.3.1 During Outage ................................................................................................................................21
4.3.3.2 During non-RF communications ...............................................................................................21
4.3.3.3 Lost Data .........................................................................................................................................21
4.3.3.4 Timing...............................................................................................................................................22
4.4 RCE REGISTERS AND TABLES AND THE CCE RESPONSE ............................................................................22
4.4.1 Programmed Into Meter...................................................................................................................22
4.4.1.1 Inbound Response Header.........................................................................................................22
4.4.1.1.1 Alarm Indicators .................................................................................................................... 22
4.4.1.1.2 Tamper Indicators ................................................................................................................. 22
4.4.1.1.3 Diagnostic Indicators ........................................................................................................... 22
4.4.1.2 EMA Registers ...............................................................................................................................22
4.4.1.2.1 “Ported” Registers................................................................................................................ 23
4.4.1.3 RCE Tables .....................................................................................................................................23
4.4.1.3.1 Command Code ..................................................................................................................... 23
4.4.1.3.2 Standard Tables..................................................................................................................... 23
4.4.1.3.3 ANSI C12.19 Manufacturer’s Tables................................................................................. 23
4.4.2 Conversion Factors ..........................................................................................................................23
5 CCE SUPPORT..................................................................................................................................................... 24
6 FCC COMPLIANCE STATEM ENT .................................................................................................................... 24
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1 AUDIENCE
This document is intended for use by customers of the RF-TWACS based AMR System,
and covers the basic principles, description of the hardware units and explanation of
operational features of DCSI’s RF solution. Additional details are available in individual
product and system level specification documents.
2 INTRODUCTION
2.1 Basic Concepts
The radio link between a water or gas meter and an electric meter is designed to be an
alternative to the present day hard-wired solution that is available for a multi-port meter
such as the IMT3-3P.
The radio link is designed to facilitate and enhance flexibility in the installation of the
AMR solution at customer premises. Although the cost of RF hardware may be slightly
higher than its hardwired counterpart, savings should result due to lower installation
costs. Any location that would be difficult or impossible to trench a line could potentially
benefit from the RF alternative.
2.2 Benefits
Aside from the overall cost savings, homeowners are delighted to learn that their yards do
not have to be dug-up, or that a cable does not have to be stapled to their siding. In
addition to the non-invasive characteristics of the installation, utilities can expect to find
the flexibility of field configurations to be one of the major advantages the RF solution.
Radio transmission means that connections need not be same-premise any more. A mix
of radio-capable and hard-wired transponders may be deployed in a given area to reduce
overall solution costs.
The system is designed to provide two main functions:
1. A “Total Consumption” reading will be frozen system-wide at a given
programmable time of day.
2. A “Present Total Consumption” will be available on-demand, updated hourly, for
each meter in the system.
2.3 Principles of Operation
Gas and water meters need to be wired to a nearby small radio transceiver unit called the
Remote Meter Transceiver (RMTR) which can be seen in Figure 1. The RMTR will
transmit data, using a UHF link, from gas and water meters to electric meters outfitted
with the EMT-3C-MP transponder, these transponders will include a plug-in radio
module board called the Electric Meter Transceiver (EMTR) that serve as TWACS
gateway, please refer to Figure 2 . The system is intended to be compact, reliable and
easy to install. It will therefore make maximal use of the RF network created by the
transmitters and receivers – regardless of property boundaries.
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Figure 1 – Front View of the Remote Meter Transceiver RMTR
Figure 2 – Electric Meter Transceiver (EMTR) board with dipole antenna and four-pin connections
to the EMA
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The installer has the latitude to create any workable network on site, and is able to
confirm that it functions prior to leaving the site. A hand-held radio tool called the Hand-
Held Transceiver (HHTR) is available to support installation, configuration, change-outs
and other field operations. An HHTR is shown in Figure 3.
Figure 3 – Hand-Held Transceiver (HHTR) Front View
Frequencies between 902 MHz and 928 MHz are used. This part of the UHF radio
spectrum is known as the 900 MHz Industrial, Scientific and Medical band (ISM) and is
unlicensed. DCSI’s radio devices operating in this band comply with FCC regulations
and rules. The radio link is a two-way half duplex, uses pseudo-random sequence
frequency hopping spread spectrum technology, and FSK modulation. All transceivers
include an integral received signal strength indicator (RSSI), obtain receipt verification,
and perform automatic retries of failed communications.
A frequency hopping algorithm is used to: comply with FCC regulations, reduce potential
interference to and from other services operating in the same band, reduce the likelihood
of eavesdropping, and to minimize the effects of selective fading.
The RMTRs do not run continually. Instead, they run only in response to external events
that cause power to be applied to its microprocessor. When the external event has been
dealt with, the power is turned off from the microprocessor. This is done to extend
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battery life. They also assembly RF data packets that contain a unique transmitter serial
number, the present reading, diagnostic information, and error-detection codewords.
A block diagram of the system can be seen in Figure 4 below.
( ( ( ) ) ) ( ( ( ) ) )
Figure 4 – Block Diagram for DCSI’s RF based AMR System
3 SYSTEM NOMENCLATURE
The nomenclature normally employed for the TWACS product line needs a little
clarification at this point.
The Remote Communication Equipment (RCE) is called an Electronic Metering
Assembly (EMA) in this instance, and is not simply a single electronic module that has
been retrofitted to an existing electric meter, but it also includes a radio transceiver
(EMTR) with its own microcontroller and is powered by the electric meter.
External to the electric meter, and connected to the gas or water meters, is another DCSI
radio transceiver module (RMTR). It houses a battery, folded dipole antenna, RF
circuitry, RF engine code, microcontroller, and cable to the remote metered device.
Please refer to Figures 5a and 5b.
E
Water
SCE
CCE
Powerline TWACS
Telephone or
Radio Voice Grade
Channel
RMTR Transceivers
EMTR and
Transponder in the
electric meter
housing.
UHF Radio
Link
Gas
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Figure 5a Figure 5b
Figures 5a and 5b – a) Rear view of the RMTR without cover showing the battery. b) RMTR board
showing the RF circuitry, folded dipole, microcontroller and reed relay.
Finally at the bottom of the hierarchy is the remote metering device (gas or water) from
which data is obtained. None of the meters are DCSI devices, however it is possible that
certain instances of EMA integration may cause DCSI to supply some of the services for
the electric meter (such as hosting the LCD). Please see Figure 6 for a better
understanding of the naming convention adopted for the hardware units.
Transponder “RCE” type equipment made
by DCSI
Radio Transceivers
( ( ( ) ) )
Figure 6 – EMA, EMTR, and RMTR Hardware Modules
This product includes a Schlumberger Centron Solid-State Electric Meter, outfitted with
our EMT-3C-MP EMA module, and the optional EMTR plug-in RF board, all under the
same meter canopy. The RMTR connects to a gas or water metering device which is
Electric Meter
EMA
EMTR
RMTR
Water or Gas Meter
with Pulser or Dial
-
encoder
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either a pulser or dial encoder. The RMTR is external to the gas or water meters, and for
adequate radio coverage must be mounted elevated above the ground, possibly on a wall.
Product Related Terms
CCE, Central Communication Equipment. Also referred to as the “Master Station”, the
current model sold to customers is called TWACS Net Server (TNS).
EMA, Electronic Metering Assembly. This can be viewed as either the traditional
“transponder module” or merely as the function in a consolidated assembly that serves as
the TWACS gateway.
EMT-3C-MP, Electric Meter Transceiver Multiport. Also called the EMA, Centron MP,
RCE or transponder.
EMTR, Electric Meter TRransceiver. This unit serves as the RF gateway between the
RMTR and the EMA. This unit continually scans channels, listening for communication
from an RMTR.
HHTR, Hand Held TRansceiver. This hand-held test tool is used to monitor RF traffic,
force link-assignments, as well as facilitate installations and change-outs.
IED, Intelligent End Device. This is an IEEE term. The end device in this case is a
metering device. It may or may not have much intelligence. If the meter is a solid state
meter, or some other metering device that supports two-way electronic communication,
such a device could be termed an “Intelligent End Device.”
RCE, Remote Communication Equipment. Historically known as the “Transponder”, the
RF project affects 3 different types of Remote Communication Equipment: the EMA,
EMTR and the RMTR. If any one of them now had to be called a “transponder” it should
be the EMA since it serves as the TWACS gateway. All of them can still be considered
RCE’s. Transponders are two-way powerline devices while transceivers are two-way
radio devices.
RMTR, Remote Meter TRansceiver. A module separate and distinct from the gas or
water meter that contains a connecting cable, microprocessor, RF circuitry, battery, and
antenna. It normally sleeps, and occasionally wakes to establish an RF link with an
EMTR. It maintains or obtains meter readings and conveys them to the EMTR.
SCE, Substation Communication Equipment. Also known as the “Substation”, the
current model sold to customers is based on the “93-CRU.”
Communication Related Terms
Channel, The selected RF band (902 to 928 MHz) gives opportunity for 79 channels
within the band. The DCSI RF TWACS system makes use of 50 channels. FCC limits the
amount of energy that can be emitted in a given channel for a certain length of time. The
transceiver design has one antenna that the transmitter and receiver portions of the circuit
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must alternately share. (The same unit cannot simultaneously transmit on one frequency
while receiving on another). This causes all two way communication to be half duplex.
FSK, Frequency Shift Keying. Modulation technique where‘1’/’0’ transmission occurs
by means of frequency shifting. One frequency is used to represent the logical ‘1’ and a
different frequency to represent the logical ‘0’.
Link, A path between two units in a communications system.
Manchester encoding, A signal transmission method defined for the representation of
binary data bits on the radio channel. Manchester encoding specifies two “half-bits”, so
that a guaranteed mid-bit transition occurs in the transmitted signal.
RSSI, Received Signal Strength Indicator. This feature available in the receiver portion
of the circuit measures the strength, relative to a noise background, with which a signal
is obtained.
RX, Receive / Receiver.
Session, A series of transactions exchanged between two units in a communication
system within each other communications zone.
TR, Transceiver
TX, Transmit / Transmitter
Data Related Terms
Frozen Read, The transponder sees many readings in the course of a day. It can be
programmed to save one of them as the official “frozen read” for a given time of day. In
the case of a hard-wired solution, the read can be performed at a set time of day. For an
RF link, the end devices are set to perform a read at the appointed time, then transmit it
some time later during the hour. The receiver in turn captures the transmission time-
stamped nearest the appointed time and applies it as the “frozen read”.
Interval Read, Is the relative amount of consumption registered by the metering device
over an interval of time. The standard interval for this design is 1 hr. Therefore, we speak
of hourly interval data – the amount of consumption that occurs in one hour time.
Present Read, The most up-to-date reading available from the meter. For an integrated
module such as an EMA, the energy consumption can be obtained immediately. For cases
where the TWACS gateway is not integrated within the meter being read, there is a
certain amount of data latency. In the case of the RF link, the system should broadcast an
update hourly. The “present read” then becomes at most one hour old, and on average a
half hour old.
Shifted Read, In metering terminology, when a copy is made of a register, it is called
“shifting.” The idea is that a snapshot of a given register is made by copying the present
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value of a dynamically moving register into a static register. Both the “present read” and
“frozen read” represent shifted readings.
Total Consumption (TC), Is the total amount of consumption registered by the device
since installation. Rollover of the count (to zero) may occur at some point during the life
of the product. Units of measure vary by service and model.
STU, Serial Time Unit. Is the unit of measure for DCSI’s proprietary Serial Time system.
Serial Time measures the number of 2.5 second intervals after midnight. Midnight
(00:00:00) corresponds to “0 STUs”. Five seconds after midnight (00:00:05) corresponds
to 2 STUs. Likewise the Serial Date is the number of days after Jan 1, 1900. This differs
from the commonly used units for time. The ANSI C12.19 standard supports a variety of
methods, the nearest ones of which measure the universal (GMT) time since midnight Jan
1, 1970 in minutes, or the local time since midnight in seconds.
4 SYSTEM OVERVIEW
4.1 General System Theory Overview
The RF link between TWACS transceivers uses a range of frequencies between 902 MHz
and 928 MHz. This range is divided into 79 channels. Fifty channels are needed to satisfy
the FCC’s minimum channel set requirements, so 50 of the 79 were chosen for use.
Five of these 50 channels are reserved for link acquisition and the other 45 are used for
link maintenance (packets transmitted after a link has been acquired). The acquisition
channels are spaced evenly throughout the upper end of the 50-channel set. The 45 link
maintenance channels are used in a random manner while a link is active between
transceivers.
The radio transceivers are equipped with folded dipole antennas. Folded dipoles were
chosen because of their broader radiation pattern as compared with regular dipoles, this
guarantees a better radio coverage under a variety of field installation conditions utilities
may find.
Operationally, TWACS transceivers can play one of two roles during an RF session: A
transceiver that requests a link is the requestor transceiver. A transceiver that replies to
that request is an acceptor transceiver.
TWACS transceivers can be characterized by their roles as shown in Table 1:
Transceiver Type Can request a link from… Can grant a link to…
EMTR Acceptor None an RMTR or an HHTR
RMTR Requestor an EMTR or an HHTR None
HHTR Both an EMTR an RMTR
Table 1 – Roles of DCSI’s Radio Transceivers
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As can be seen, EMTRs never request a link; they are always acceptor transceivers. By
contrast, RMTRs never grant a link; they are always requestor transceivers. The HHTR,
since it must be able to communicate with both EMTRs and RMTRs, can act as either an
acceptor transceiver (with an RMTR) or a requestor transceiver (with an EMTR).
The reason this distinction is important is that the acceptor transceiver always controls
the channels hop sequence. This means that an EMTR always controls the hop sequence.
An HHTR controls the sequence when communicating with an RMTR. An RMTR never
controls the hop sequence.
Bear in mind that this distinction between acceptor and requestor transceivers is strictly
operational. It is not a functional difference because the same RF transceiver and RF
engine code are used on all transceivers.
The RMTR is a battery powered device. In order to maximize battery life, the RMTR is
powered off as much as possible. The requirement to maximize battery life drives a
number of other factors in the system. One implication of this is that the normal
Master/Slave relationship, evident throughout the design, which begins at the CCE, now
ends at the EMTR. The EMTR cannot wake up the RMTR to establish a session, but can
take control of a session once it is established by the RMTR.
The RMTR is designed to wake up once an hour and create a session with an EMTR.
Any unknown data is uploaded at that time from the RMTR to the EMTR. At any given
time, the EMTR knows nearly everything the RMTR knows, plus it maintains
engineering data to describe the quality of the radio link. The CCE may access this data
upon demand.
The EMTR maintains an “acquisition list” table. Each RMTR is categorized as belonging
to a certain type of service. The various types are: Electric, Water, Gas, and Propane. A
number of ports are supported for each service type. The CCE reads data from the
appropriate port in order to obtain information.
4.2 RF Hardware Specifications, Installation, Operations & Maintenance
4.2.1 Centron Meter
In addition to supporting TWACS communication, the EMT-3C-MP module hosts the
LCD and the metering components from Schlumberger. The EMA also supports the
connection to the EMTR board which is housed under the same canopy, this is shown in
Figure 7. Figure 8 shows the EMT-3C-MP transponder integrated with an Schlumberger
solid state Centron electric meter.
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Figure 7 - EMT-3C-MP board hosting the Centron’s LCD/Metering Components and the EMTR RF
Board
Figure 8 – Schlumberger Centron + EMT-3C-MP Assembly
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4.2.1.1 Initial Installation and Change-outs
The installation of a Centron meter that is integrated with the EMT-3C-MP TWACS
module is handled like any ordinary meter change-out. The installer must record the final
reading of the meter that is removed, replace it with a Centron meter that is outfitted with
a TWACS module, record the customer number, date, initial reading, and meter serial
number. Other data items may be required as part of the utility’s data process.
Once the data from the installer has entered the CCE, the integrated assembly will be
“searched”, and the electrical path to the unit determined. Additional steps will be taken
to set it up as part of the daily electric meter AMR process.
4.2.2 Remote Meter (gas/water) Transceiver (RMTR)
4.2.2.1 RMTR Specifications
Power Source: 3.6 Volts battery
Design Operational Lifespan:
Minimum: 10 years
Expected: 15 years
Communication Range: 1200 ft. open field @ max. power amplifier gain
Frequency of Operation: 902 to 928 MHz
Number of Channels: 5 link acquisition + 45 link maintenance, bi-directional
Frequency Selection: Pseudo-random Frequency Hopping Spread
Spectrum. (The link acquisition channels are not
part of the hopping sequence).
Signal Strength Indicator: Integral Received Signal Strength Indicator (RSSI).
Clear Channel Selection Method: Walkthrough acquisition channel list in ascending
order, and then use the quietest. Occupied channels
are immediately passed over.
Clear Channel Signal Strength Criterion:The RMTR finds the quietest channel by tuning to
each and recording the RSSI, the channel with the
lowest RSSI is used.
Gain Control: 3 discrete auto-adjustable levels of transmitter
power.
Acquisition Retry Limit: All transmissions comply with FCC limits. This
includes the acquisition process. Acquisition is
attempted on each channel at each power level.
TX Power Amplifier Gain: A value is maintained by the RMTR that records the
level used for the last successful transaction. This
value is used until an RF session has failed and a
successful session is acquired with a new power
level. All packets are transmitted at this level until
every acquisition channel has experienced the retry
limit. After one cycle through the channels, the gain
is increased to the next level (if available) and the
channels cycled again.
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Data Flow: Asynchronous, half duplex.
Data Format: 8N1
Modulation: FSK
Coding: Manchester encoding (3200 bps)
Data Rate: 1600 bps
Data Encryption: DCSI proprietary method #1
Maximum Packet size: Complies with FCC rules.
Max. Packet Transmission time: Complies with FCC rules.
4.2.2.2 Initial Installation and Change-outs
When an RMTR is installed, it must be configured for operation.
The installer must note the:
• Serial Number of the RMTR that is installed
• Date
• Customer number
• Initial dial reading
• Meter type
• Service Type
• Number of dials
• The unit of measure as displayed on the dial face
• The multiplier to convert pulses to a valid dial reading
• Any other items required by the utility’s process
The installer, using an HHTR must configure the RMTR as to the:
• Service Type (Water / Gas)
• IED configuration (Encoder vs. pulser operation, selecting the appropriate
supported model).
• Number of dials
Once the RMTR is installed, a nearby EMTR must be selected by the installer to convey
the data. The installer must use the HHTR tool to make this assignment in the EMTR.
The installer should test the system after all of the devices have been configured. The
installer can use the HHTR to cause the RMTR to initiate a data upload to the EMTR.
The tool will confirm that the test was successful.
The change-out process is just like a new installation of the RMTR described above, with
the exception that any previous EMTR assignments should be reused, or accounted-for,
with the use of the new RMTR.
4.2.2.3 RMTR Operations
The RMTR wakes up once an hour (hourly after the freeze time; for example: if the
freeze time is at 9:15 actual time, then hourly updates will occur at 10:15, 11:15, and so
on) to obtain a reading and updates its present total consumption register. In the case of a
dial encoder it wakes up once an hour to read the encoder then write a table. In the case
of a pulser it wakes up to record a pulse event, and also once an hour (relative to the
freeze time) to update the table.
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The transmission of data from the RMTR to the EMTR follows this sequence:
1. The RMTR wakes up once an hour and attempts to create a session with an EMTR in
order to upload readings and tamper information. The RMTR attempts to create a
session on a quiet channel using a low-power amplifier-gain. After each Request-to-
Send (RTS) packet is transmitted, the RMTR listens on the return frequency of the
same channel for an acknowledgment to indicate acquisition by a suitable EMTR.
The acknowledgment contains the EMTR’s serial number so that a certified link can
be established.
Acquisition Sequence:
The RMTR attempts to acquire a session by transmitting an RTS packet on the
clearest channel at the same power level of the last successful session (in the case
of a first time acquisition, it begins with the lowest power level). If this
acquisition fails, it tries each of the remaining 4 acquisition channels at that power
level, then, if the attempt on each channel fails, it will increase power to the next
higher power level. After cycling through each of the channels and escalating up
to the highest power level (attempting as many as 15 retries), it will go back to
“sleep” and reattempt later.
2. If the link is accepted by the EMTR, it replies with a confirmation packet including
the RMTR’s serial number in the transmission, forming a “source - destination”
routing packet.
3. The data field in all packets is encrypted for security purposes.
4. After the EMTR accepts the link, it takes control of the session and issues commands
to harvest data.
5. The EMTR informs the RMTR that it is has completed all necessary exchanges by
sending a “completion” message to the RMTR. This message is important to the
RMTR, without it the RMTR must assume that a jam has occurred and that the data
upload must be retried at a later time on another channel beginning with the first
exchange.
Figure 9 below shows a state diagram that summarizes the described operations.
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Figure 9 – State Diagram for the RMTR
4.2.2.4 RMTR Maintenance
The RMTR requires a battery change-out approximately once every 15 years. Expended
batteries should be disposed of in accordance with local regulations. Battery voltage
levels may be remotely checked by the CCE.
4.2.3 Electric Meter Transceiver (EMTR)
4.2.3.1 EMTR Specifications
Power Source: EMT-3C-MP power supply
Communication Range: 1200 ft. open field @ max. power amplifier gain
Frequency of Operation: 902 to 928 MHz
Number of Channels: 5 link acquisition + 45 link maintenance, bi-directional.
Frequency Selection: Pseudo-random Frequency Hopping Spread
Spectrum. (The link acquisition channels are not
part of the hopping sequence).
Signal Strength Indicator: Integral Received Signal Strength Indicator (RSSI).
Occupied Channel Selection Method: Walkthrough channel list in ascending order. RTS
packets from a suitable RMTR, or HHTR are
accepted. Any other traffic causes the EMTR to
immediately abandon the channel and move on.
Gain Control: 3 discrete auto-adjustable levels of transmitter
power.
TX Power Amplifier Gain: The EMTR reciprocates with the same Tx Gain that
the Requesting device uses.
Data Flow: Asynchronous, half duplex.
Data Format: 8N1
Modulation: FSK
Sleep
“Dotting”
Valid
Session
Timeout occurs, or
ACK received from a disallowed EMTR/, or
ACK is addressed to a different RMTR/
Timeout or
“COMPLETION”/
Awaken
with
message/
“ACK” received from
allowed EMTR / send
acknowledgement confirming
link is established.
Command
received from
EMTR /
transmit more
data
NAK received/
retry packet
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Coding: Manchester encoding (3200 bps)
Data Rate: 1600 bps
Data Encryption: DCSI proprietary method #1
Maximum Packet size: Complies with FCC rules.
Max. Packet Transmission time: Complies with FCC rules.
4.2.3.2 Initial Installation and Change-outs
The intent of this section is to provide general guidelines for the initial installation and
subsequent troubleshooting and replacement of EMTR units.
A Centron meter that has been outfitted with the EMT-3C-MP and EMTR modules is
both TWACS and RF-TWACS capable. If they are deployed in advance of the RMTRs,
then the electric metering capability of the Centron meter may still be used prior to
deployment of any gas or water metering.
If a Centron meter has been initially deployed without an EMTR, it always can be
converted later, at the meter shop, to a radio-capable unit by plugging in an EMTR and
properly initializing the assembly.
The change-out procedure for a failed EMTR is the nearly same as described below in
Section 4.2.4.2.3 – EMTR Installation. If the installer finds that the EMTR is still alive, it
is advisable that he use the HHTR to first upload the “Acquisition List” table from the
unit, swap it out, then download the same Acquisition List into the new unit.
If on the other hand, the installer finds that the EMTR is not functional, he must treat this
as a new installation and load the Acquisition List with the proper assignments. The only
way to know for sure which assignments are necessary is for him to be armed with this
information from the CCE before he goes out into the field. All RMTRs that were
assigned to the old EMTR need to be assigned to the new EMTR (or other EMTRs) in
order to restore network integrity.
4.2.3.3 EMTR Operations
Creation of a Session
The EMTR scans acquisition channels and determines the average RSSI energy level. If
the EMTR hears a channel which contains energy significantly above the average, it stops
on that channel and attempts to establish communication. If it cannot do this successfully,
the EMTR abandons the channel and resumes scanning. If it decodes a valid packet, and
it is an RTS from an HHTR or from an RMTR for which it is responsible, it replies with a
Clear-to-Send (CTS) packet or with a valid command packet.
Data Transmission
After the EMTR accepts the RTS, it takes control of the session and issues commands to
harvest data.
Additional exchanges may occur between the two devices, limited only by FCC rules.
The data field in packets is encrypted (with the exception of RTS and CTS packets).
Session Conclusion (with an RMTR)
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The session normally ends with a disconnect command.
The session abnormally ends whenever a packet exchange fails and the retry mechanism
is exhausted.
Maintenance Session (with an HHTR)
The HHTR maintains control of the session and can exchange (read and write) any
allowable data with the EMTR. The session concludes under HHTR control and ends
with a disconnect command.
Data Retention
Data is retained in the EMTR until new data is uploaded during an RMTR session or an
RMTR has been removed from the acquisition list.
4.2.3.4 EMTR Maintenance
There are no batteries in the EMTR, nor is any normal maintenance required. If however,
RMTR’s are installed or removed in the area, an EMTR within range must be configured
to accept it. The “Acquisition List” maintained in the EMTR must be modified to allow
the EMTR to accept session requests from the RMTR. The Acquisition List can be
updated by the installer using the HHTR.
4.2.4 Hand-Held Transceiver (HHTR) – Verification and Installation Tool
4.2.4.1 HHTR Specifications
Power Source: Six rechargeable AA batteries with a minimum life of 8 hours of
continuous use. (Figure 10)
Operating Modes: Work Order Entry – Field Installation Data Collection
RMTR
Configure – Configures IED
Replace - Swap-out an old RMTR with a new one.
Status – IED Configuration and battery status
Install – Add an RMTR to an EMTR’s acquisition list.
Communication Status – RSSI, Engineering data, IED
configuration and battery status
Review – Review what was just done for the present order
number.
EMTR
EMTR Replace – Swap-out an old EMTR with a new one
(uploads the acquisition list from the old unit and
downloads it to the new EMTR).
View Acquisition List – Retrieves acquisition list from the
EMTR and displays how they are mapped internally
Remove RMTR from Acquisition List – Deletes entry.
Serial Port – Isolated RS232 compliant port to logic-level
RS232 level shifter
TWACS
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HRTS – HRTS functionally equivalent installation tool
HHTR Configuration: Interface
RS232 Logic level inverted (True / False)
Keypad beep (Enabled / Disabled)
I/O port (Indicator / Control)
Power Configuration: LED backlight timer
Power off timer
Battery / charging status
Information: Firmware Revision and Password Protected FCC Compliance Code
Device Self Test
RF specs: Same as the EMTR / RMTR
Display: LCD
Keypad: 16 button keypad
Figure 10 – HHTR battery compartment
4.2.4.2 HHTR Operation
The Hand Held Transceiver (HHTR) has a number of applications:
• RMTR Configuration
• RMTR Network Insertion
• EMTR Installation
• Site surveys
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• Transceiver equipment diagnostics
• Installation Data Collection
• Other applications
4.2.4.2.1 RMTR Configuration
The RMTR must be either factory or field configured prior to successful operation. The
RMTR is equipped with a reed relay that can be engaged in the field by swiping a magnet
included in the HHTR, once the reed relay is engaged, the RMTR energizes its processor
and is ready for a configuration session with the HHTR
Figure 11 below shows the application setup:
( ( ( ) ) ) ( ( ( ) ) )
Figure 11 – RMTR Configuration Setup
The HHTR supports new RMTR installations by allowing field configuration of the
device regarding meter type, number of dials, type of service, an IED device ID, etc.
4.2.4.2.2 RMTR Network Insertion
EMTRs contain the network equivalent of “routing tables” that must be maintained.
Operation of the system in the forced-link assignment mode places the burden of network
maintenance on the part of the installer.
Figure 12 summarizes the setup for this application:
HHTR RMTR
Metering Mechanism
Pulser or
Dial
Encoder
Magnet
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( ( ( ) ) ) ( ( ( ) ) )
( ( ( ) ) )
Figure 12 – Setup for Insertion of an RMTR unit to the Network
The HHTR must know the serial number of any old RMTR that must be removed from
the network, the S/N of the new RMTR, and the S/N of the EMTR. Following the
configuration of the new RMTR, the HHTR can (without travel on the part of the
installer) acquire the EMTR, update it’s table, reacquire the new RMTR, cause it to
become “unsatisfied” regarding its upload, disconnect, and observe the traffic between
the RMTR and EMTR.
The new RMTR must be inserted in the acquisition list matrix in the appropriate column
(corresponding to the service type.) Within that column, the RMTR must be inserted in
the first available port. This would be the port with the smallest number with a zeroed
serial number.
4.2.4.2.3 EMTR Installation
At some point both RMTRs and EMTRs will be present in the same area. The Serial
Number of every RMTR to be assigned to the new EMTR must be entered, and the
service type of the RMTR known as well. Forced assignments can be made by writing to
the acquisition list table in the EMTR.
If the old EMTR is still functional, the original tables may be uploaded to the HHTR
prior to removal of the old EMTR. After EMTR replacement, the stored acquisition list
may be downloaded to the new EMTR and operation may resume. The installer may wish
to initiate an upload from a nearby RMTR to test the network.
4.2.4.2.4 Site Survey
An RF site survey is a characterization of a particular installation location from a radio
propagation stand point. It’s an essential element for proper operation of an RF data
collection system. Site survey includes a comprehensive test at the customer site that will
analyze the environment and check for any potential interference. Upon completion, the
study will determine best location of antennas and RMTR devices needed for optimal
coverage.
EMTR RMTR
Metering Mechanism
Pulser or
Dial
Encoder
HHTR
EMA
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There are many different ways to evaluate a site. Some are listed below:
1. The HHTR may be used to harvest engineering data from an EMTR which has
collected a history of previous RF communications with a particular RMTR. The
Engineering Data register is an 8 bytes register that allows assessment of the radio
link quality. Information contained in this register includes: Last Power Amplifier
Gain, Last Channel, Last RSSI, Channel Abandonment, Acquisition Failures,
Error Codes for Last Failure and a 24 Hour Acquisition Log.
2. The HHTR may be used prior to transceiver installation to evaluate a given site.
HHTRs and special RMTRs may be positioned in various locations to evaluate
signal strength and quality.
Commercially available test tools are available for RF Site Survey, but direct use of the
HHTR product itself reduces the amount of tools that an installer must carry.
4.2.4.2.5 Transceiver Equipment Diagnostics
New installations as well as problematic ones will require on-site troubleshooting. (A
need also exists for a meter-shop test-tool). The HHTR can be used to exercise
transceivers. The HHTR is able to read the device tables, including the Engineering Data
tables. The HHTR can initiate an exchange between field devices.
The HHTR will be able to read the EMTR or RMTR tables to investigate a problem.
Certain tables indicate device status. Other tables, provide AMR data. The Engineering
Data field from the Acquisition List can be particularly helpful in analyzing historical
communcation performance.
4.2.4.2.6 Installation Data Collection
When a new RMTR is installed, the EMTR raises a diagnostic flag that causes the CCE
to read tables and discover the port number, serial number, and other associated account
information. The HHTR may collect installation data that serves to collaborate with
information discovered via TWACS.
4.2.4.2.7 Other HHTR Applications
Other possible applications of the Hand-Held Test Tool Are:
• RCE Functional Testing
• Manufacturing and Integration Tests
• Emulation of older Test Tools (HRTS)
• Upgrade Transceivers Firmware
4.2.4.3 HHTR Maintenance
Batteries must be recharged daily.
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4.3 RF-TWACS System Software – Central Communication Equipment
4.3.1 Data Available From Meters
The system is designed to supply a total consumption reading from each meter that has
been frozen at a specific time of day on a daily basis. Furthermore, the system can deliver
at any time, an “on-demand” or “Present” total consumption reading for each meter. The
“present” gas or water reading will be pulled from the electric meter. The data in the
electric meter is updated hourly.
4.3.2 CCE Data Requirements
4.3.2.1 Initial Installation
The CCE need only know that an EMA with RF capability has been installed. It will
“search” the meter and install it into a daily AMR schedule. If and when RF-TWACS
devices are installed at the same location, and the installer configures an EMTR (and
consequently the hosting EMA) to accept an RMTR, a flag will be set indicating a change
in the configuration tables. The CCE may then read various registers to self-discover the
type of service and serial number of the RMTR.
4.3.2.2 Change-outs
The requirements are the same as for initial installation.
4.3.3 Data Availability
4.3.3.1 During Outage
Data cannot be conveyed over the TWACS system during an outage. RMTR’s will
attempt to upload data to EMTR’s using RF, but be unsuccessful because EMTR’s are
powered from the powerline.
4.3.3.2 During non-RF communications
As described earlier, radio communications are kept to a minimum in an effort to
preserve battery life. The EMTR and EMA maintain data on behalf of the RMTR. The
design intends for data to be updated every hour. The latest RMTR data is readily
available from the EMA via the TWACS.
4.3.3.3 Lost Data
It is possible that in some instances, RF conditions will prevent communications from
occurring between an RMTR and an EMTR every hour. In this case the “present total
consumption” reading maintained in the EMTR will be the last successful reading, not
the latest top-of-the-hour present reading.
It is possible that the frozen daily read can be affected by adverse RF propagation
conditions. In this case, the frozen daily read will be obsolete until radio communication
is restored.
Once RF communication is restored, the “present” total consumption reading will be
updated in the EMTR, and if necessary, the daily frozen reading as well.
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4.3.3.4 Timing
The “Present” total consumption reading (updated hourly) is available at any time. The
Daily Frozen total consumption reading is available for 23 hours during the day. The
CCE must give the RCE time to move the frozen read up to the EMA. For this reason,
harvest of the frozen reading must not begin until one hour after the service freeze time.
Harvesting can continue for the next 23 hours -- until the service freeze time rolls around
the next day.
4.4 RCE Registers and Tables and the CCE Response
4.4.1 Programmed Into Meter
4.4.1.1 Inbound Response Header
Important status flags are contained in the EMA response header byte which serves as a
preamble in every TWACS inbound response from an RCE. The header includes Alarm,
Tamper, and Diagnostic Indicators.
4.4.1.1.1 Alarm Indicators
Among the supported alarms are:
• The RMTR associated with this action indicates a near-term battery failure.
• The RMTR associated with this action indicates imminent battery failure.
• The port associated with this action is obsolete. (Obsolete is defined to mean
“Unassigned”.)
• Forced-assignment acquisition list maintenance has occurred. (This bit is cleared
by writing ‘0’).
4.4.1.1.2 Tamper Indicators
Among the supported alarms are:
• The associated RMTR was unplugged from its meter or IED and has now been
reconnected.
4.4.1.1.3 Diagnostic Indicators
Among the supported alarms are:
• EMA Hardware failure.
• EMA to EMTR Communications failure.
• EMTR Hardware failure.
• EMTR to RMTR Communications failure.
• The RMTR associated with this action has reported a hardware failure.
• RMTR to IED communications failure.
• The IED (meter, dial-encoder, or in some cases, pulser) associated with this action
has reported a diagnostic error or has behaved illegally.
4.4.1.2 EMA Registers
The data is exchanged between the CCE and EMA by means of “RCE Read Register”
and “RCE Write Register” commands. The “MultiPort” series of RF capable
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transponders organizes data in a series of “register files.” Each register-file is a series of
ports with consecutive (and therefore calculable) addresses.
4.4.1.2.1 “Ported” Registers
The following registers are arranged in a register file form to permit register number
computation by “port number” and service type:
• RMTR Serial Number, and Product Number
• Present Total Consumption
• Frozen Total Consumption
• RMTR Status
• RMTR RF Engineering Data
4.4.1.3 RCE Tables
This design endeavors to fully support the transport of ANSI C12.19 tables, while at the
same time deploying a minimally C12.19 compliant implementation. Full compliance
becomes possible when the Intelligent End Device (IED) that meters the commodity
becomes C12.19 compliant.
4.4.1.3.1 Command Code
The following commands are supported at a minimum within the RF-TWACS protocol in
an effort to support ANSI C12.19 compatibility:
• Read Entire Table
• Read Partial Table using Offset method
• Write Entire Table
• Write Partial Table using Offset method
4.4.1.3.2 Standard Tables
• Table 00, General Configuration
• Table 01, General Manufacturer’s Identification
4.4.1.3.3 ANSI C12.19 Manufacturer’s Tables
ANSI C12.19 Manufacturer’s Table numbers range from 2048 to 4095. Note that the first
of these is known as table number 2048, and also manufacturer’s table number zero.
• Table 2048, MFG_ID
• Table 2049, 24 Hour Interval Data Table
• Table 2050, Unsatisfied-Daily-Frozen-Read Countdown
• Table 2051, RMTR Configuration
• Table 2052, RMTR Status
• Tables 2176-2207, Acquisition List
4.4.2 Conversion Factors
A consumption reading is usually conveyed in pulses, and requires multiplication by an
appropriate scaling factor to be converted to a billing unit of measure. It is important that
the installer of the RMTR keep good records regarding the type of unit that it is
connected to. This data must be conveyed to the CCE so that it can choose the
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appropriate scaling factor. The installer must also indicate the number of dials on the
meter. The CCE can use this information to recreate the dial face reading as it is in the
field.
5 CCE SUPPORT
a. If any type of RMTR or appropriate EMTR installation (or change-out) occurs, the
installer is required to update the Acquisition Table in the EMTR. This in turn causes
a flag to be raised in the RCE Inbound Header, and a bit in internal Register #34,
Indicator Alarm to be asserted.
b. The CCE reads the “Port Quantities by Service” internal register #751, and
determines how many ports are in use for each service.
c. The CCE can then self-discover the Serial Number of the RMTR for each port
assignment. The CCE reads the MFG_ID registers (#800-831) and saves the
information in a database for future reference.
d. Other associated information such as RMTR configuration data can be obtained by
additional register reads.
The installer should have independently recorded the serial numbers of any equipment
added or removed to the system. The CCE must support the process of determining the
presence or absence of serial numbers. If equipment is added and doesn’t subsequently
appear in the network, the cause must be evaluated. Some possible reasons are:
1. This is the first equipment (either RMTR or EMTR) in an area. It takes both in the
same area for communication to occur. (A note by the installer should indicate
this.)
2. The equipment is out of range. (An on-site test should have confirmed proper
operation before the installer left.)
3. Unreliable communications. Perhaps RF is not the right solution for this site.
4. Equipment failure. (This should be exceptionally rare in light of the stringent
manufacturing QA and the on-site test by the installer.)
The CCE must compare the list of all units that have been installed to the list of units that
are operational. If the lists are not the same, it needs to be investigated.
The CCE should be able to produce an acquisition list relationship table for use by the
installers. If a given RMTR is to be swapped out, the list allows the installer to reproduce
the (forced) ling-assignments in the original equipment.
6 FCC COMPLIANCE STATEMENT
a. Changes not expressly approved by Distribution Control Systems, Inc. could void
the user’s authority to operate the equipments.
b. Note: The equipments have 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. These equipments generate, use and can radiate radio
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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
these equipments do cause harmful interference to radio or television reception,
which can be determined by turning the equipments off and on, the user is
encouraged to try to correct the interference by one or more of the following
measure:
- Reorient or relocate the receiving antenna.
- Increase the separation between the equipments and receiver.
- Connect the equipments into an output on a circuit different from that to
which receiver is connected.
- Consult the dealer or an experienced radio/TV technician for help.
c. Operation is subject to the following two conditions: (1) These devices may not
cause harmful interference and (2) these devices must accept any interference
received, including interference that may cause undesired operation.
d. “To reduce potential radio interference to other users, the antenna type and its
gain should be chosen that the equivalent isotropically radiated power (EIRP) is
not more than that required for successful communication”.
------------------------------------------
Contact Information:
Distribution Control Systems Inc.
5657 Campus Parkway, Hazelwood, MO 63043
Customer Service Phone Number: 1-800-892-9008
Or Contact your Program Manager