PowerLab Teaching Series Owner's Guide (15T, 26T, 2/26, 4/26) Power Lab OG

User Manual: Teaching Series (15T, 26T, 2/26, 4/26) Manuals | ADInstruments

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PowerLab®

Teaching Series

Owner’s Guide

PowerLab Owner’s Guide

ii

This document was, as far as possible, accurate at the time of release. However, changes

may have been made to the software and hardware it describes since then.

ADInstruments Pty Ltd reserves the right to alter specifications as required. Late-

breaking information may be supplied separately.

Trademarks of ADInstruments

PowerLab®, LabChart®, LabTutor®, LabAuthor® and MacLab® are registered trademarks of

ADInstruments Pty Ltd. The names of specific recording units, such as PowerLab 15T, are

trademarks of ADInstruments Pty Ltd. LabTutor Server, Chart and Scope (application

programs) and LabTutor Online are trademarks of ADInstruments Pty Ltd.

Other Trademarks

Apple, Mac and Macintosh are registered trademarks of Apple Computer, Inc.

Windows, Windows 7 and Windows Vista are either registered trademarks or

trademarks of Microsoft Corporation.

All other trademarks are the property of their respective owners.

Product: ML818 PowerLab 15T, ML826 PowerLab 2/26, ML846 PowerLab 4/26 and

ML856 PowerLab 26T

Document Number: U-ML818/OG-003F

Part Number: 5352

Copyright © 2014 ADInstruments Pty Ltd.

Unit 13, 22 Lexington Drive, Bella Vista, NSW 2153, Australia

All rights reserved. No part of this document may be reproduced by any means without

the prior written permission of ADInstruments Pty Ltd.

Web: www.adinstruments.com

Technical Support: support.au@adinstruments.com

Documentation: documentation@adinstruments.com

ADInstruments Pty Ltd. ISO 9001:2000 Certified Quality Management System

Reg. No. 1053

Contents iii

Contents

Safety Notes 5

1 Overview 11

How to Use This Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Software Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

PowerLab Check. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

The PowerLab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

The Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Analog Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Isolated Stimulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

The Bio Amp Inputs (Inputs 3 and 4) . . . . . . . . . . . . . . . . . . . . . . . . 16

The Back Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Audio Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

I2C Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

USB Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Digital Input and Output Connectors . . . . . . . . . . . . . . . . . . . . . . . . 18

Ground Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Power Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

The Bio Amp Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Other ADInstruments Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2 Setting Up 21

The PowerLab Self-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Connecting the PowerLab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

ADInstruments Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

LabTutor Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

LabChart Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

The Isolated Stimulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Choosing How Stimulation Should Start . . . . . . . . . . . . . . . . . . . . . . 24

Choosing a Stimulus Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Creating a Custom Stimulus Waveform . . . . . . . . . . . . . . . . . . . . . . . 26

PowerLab Owner’s Guide

iv

Setting Stimulus Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Marker Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

The Stimulator Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

The Bio Amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Signal Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Setting the Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Inverting the Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

A Technical Aspects 33

How it Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

The Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

The Analog Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

The External Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Bio Amp Input (Inputs 3 & 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

The Isolated Stimulator Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

PowerLab Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Digital Input and Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

I2C Expansion Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Input Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

USB Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Earthing and Ground Loop Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

B Specifications 43

Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Pod Connectors (DIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Bio Amp Input – Inputs 3 & 4 (PowerLab 15T & 26T) . . . . . . . . . . . . . . 45

Output Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Isolated Stimulator Output (PowerLab 15T & 26T) . . . . . . . . . . . . . . . . 46

External Trigger (not on PowerLab 15T) . . . . . . . . . . . . . . . . . . . . . . 47

Expansion Ports (not on PowerLab 15T) . . . . . . . . . . . . . . . . . . . . . . 47

Microprocessor and Data Communication . . . . . . . . . . . . . . . . . . . . . 47

Physical Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Operating Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Electromagnetic Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Immunity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Separation Distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

C Glossary 51

Index 57

Safety Notes 5

Statement of Intended Use

All products manufactured by ADInstruments are intended for use in

teaching and research applications and environments only. ADInstruments

products are NOT intended to be used as medical devices or in medical

environments. That is, no product supplied by ADInstruments is intended to

be used to diagnose, treat or monitor a subject. Furthermore no product is

intended for the prevention, curing or alleviation of disease, injury or

handicap.

Where a product meets IEC 60601-1 it is under the principle that:

• it is a more rigorous standard than other standards that could be chosen,

and

• it provides a high safety level for subjects and operators.

The choice to meet IEC 60601-1 is in no way to be interpreted to mean that a

product:

• is a medical device,

• may be interpreted as a medical device, or

• is safe to be used as a medical device.

Safety Notes

PowerLab Owner’s Guide

6

Safety Symbols

Devices manufactured by ADInstruments that are designed for direct

connection to humans are tested to IEC 601-1:1998 (including amendments 1

and 2) and 60601-1-2, and carry one or more of the safety symbols below.

These symbols appear next to those inputs and output connectors that can be

directly connected to human subjects.

The three symbols are:

• BF (body protected) symbol. This means that the input connectors are

suitable for connection to humans provided there is no direct electrical

connection to the heart.

• CF (cardiac protected) symbol. This means that the input connectors are

suitable for connection to human subjects even when there is direct

electrical connection to the heart.

• Warning symbol. The exclamation mark inside a triangle means that the

supplied documentation must be consulted for operating, cautionary or

safety information before using the device.

Further information is available on request.

Bio Amp Safety Instructions

The Bio Amp inputs displaying any of the safety symbols are electrically

isolated from the mains supply in order to prevent current flow that may

otherwise result in injury to the subject. Several points must be observed for

safe operation of the Bio Amp:

• All Bio Amp front-ends (except for the ML138 Octal Bio Amp) and

PowerLab units with a built-in Bio Amp are supplied with a 3-lead or 5-

BF symbol: Body-

protected equipment

CF symbol: Cardiac-

protected equipment

!

Warning symbol: ‘see

documentation’

Safety Notes 7

lead Bio Amp subject cable and lead wire system. The ML138 Octal Bio

Amp is supplied with unshielded lead wires (1.8 m). Bio Amps are only

safe for human connection if used with the supplied subject cable and lead

wires.

• All Bio Amp front-ends and PowerLab units with a built-in Bio Amp are

not defibrillator-protected. Using the Bio Amp to record signals during

defibrillator discharges may damage the input stages of the amplifiers.

This may result in a safety hazard.

• Never use damaged Bio Amp cables or leads. Damaged cables and leads

must always be replaced before any connection to humans is made.

Isolated Stimulator Safety

Instructions

The Isolated Stimulator outputs of a front-end signal conditioner or PowerLab

with a built-in isolated stimulator are electrically isolated. However, they can

produce pulses of up to 100 V at up to 20 mA. Injury can still occur from

careless use of these devices. Several points must be observed for safe

operation of the Isolated Stimulator:

• The Isolated Stimulator output must only be used with the supplied bar

stimulus electrode.

• The Isolated Stimulator output must not be used with individual

(physically separate) stimulating electrodes.

•Stimulation must not be applied across the chest or head.

•Do not hold one electrode in each hand.

• Always use a suitable electrode cream or gel and proper skin preparation

to ensure a low-impedance electrode contact. Using electrodes without

electrode cream can result in burns to the skin or discomfort for the

subject.

• Subjects with implantable or external cardiac pacemakers, a cardiac

condition, or a history of epileptic episodes must not be subject to

electrical stimulation.

• Always commence stimulation at the lowest current setting and slowly

increase the current.

• Stop stimulation if the subject experiences pain or discomfort.

• Do not use faulty cables, or those that have exhibited intermittent faults.

• Do not attempt to measure or record the Isolated Stimulator waveform

while connected to a subject using a PowerLab input or any other piece of

equipment that does not carry the appropriate safety symbol (see Safety

Symbols above).

PowerLab Owner’s Guide

8

Always check the status indicator on the front panel. It will always flash green

each time the stimulator delivers a current pulse. A yellow flash indicates an

‘out-of-compliance’ (OOC) condition that may be due to the electrode contact

drying up. Always ensure that there is good electrode contact at all times.

Electrodes that are left on a subject for some time need to be checked for dry

contacts. An electrode impedance meter can be used for this task.

• Always be alert for any adverse physiological effects in the subject. At the

first sign of a problem, stimulation must be stopped, either from the

software or by flicking down the safety switch on the front panel of any

built-in Isolated Stimulator or the ML180 Stimulus Isolator.

• The ML180 Stimulus Isolator is supplied with a special transformer plug

pack. The plug pack complies with medical safety requirements.

Therefore, under no circumstances should any other transformer be used

with the Stimulus Isolator. For a replacement transformer plug pack please

contact your nearest ADInstruments representative.

General Safety Instructions

To achieve the optimal degree of subject and operator safety, consideration

should be given to the following guidelines when setting up a PowerLab

system either as stand-alone equipment or when using PowerLab equipment

in conjunction with other equipment. Failure to do so may compromise the

inherent safety measures designed into PowerLab equipment. The following

guidelines are based on principles outlined in the international safety

standard IEC60601-1-1: General requirements for safety - Collateral standard:

Safety requirements for medical systems. Reference to this standard is required

when setting up a system for human connection.

PowerLab systems (and many other devices) require the connection of a

personal computer for operation. This personal computer should be certified

as complying with IEC60950 and should be located outside a 1.8 m radius

from the subject (so that the subject cannot touch it while connected to the

system). Within this 1.8 m radius, only equipment complying with IEC60601-

1 should be present. Connecting a system in this way obviates the provision of

additional safety measures and the measurement of leakage currents.

Accompanying documents for each piece of equipment in the system should

be thoroughly examined prior to connection of the system.

While it is not possible to cover all arrangements of equipment in a system,

some general guidelines for safe use of the equipment are presented below:

Safety Notes 9

• Any electrical equipment which is located within the SUBJECT AREA

should be approved to IEC60601-1.

• Only connect those parts of equipment that are marked as an APPLIED

PART to the subject. APPLIED PARTS may be recognized by the BF or CF

symbols which appear in the Safety Symbols section of these Safety Notes.

• Only CF-rated APPLIED PARTS must be used for direct cardiac

connection.

• Never connect parts which are marked as an APPLIED PART to those

which are not marked as APPLIED PARTS.

• Do not touch the subject to which the PowerLab (or its peripherals) is

connected at the same time as making contact with parts of the PowerLab

(or its peripherals) that are not intended for contact to the subject.

• Cleaning and sterilization of equipment should be performed in

accordance with manufacturer’s instructions. The isolation barrier may be

compromised if manufacturer’s cleaning instructions are not followed.

• The ambient environment (such as the temperature and relative humidity)

of the system should be kept within the manufacturer’s specified range or

the isolation barrier may be compromised.

• The entry of liquids into equipment may also compromise the isolation

barrier. If spillage occurs, the manufacturer of the affected equipment

should be contacted before using the equipment.

• Many electrical systems (particularly those in metal enclosures) depend

upon the presence of a protective earth for electrical safety. This is

generally provided from the power outlet through a power cord, but may

also be supplied as a dedicated safety earth conductor. Power cords should

never be modified so as to remove the earth connection. The integrity of

the protective earth connection between each piece of equipment and the

protective earth should be verified regularly by qualified personnel.

•Avoid using multiple portable socket-outlets (such as power boards)

where possible as they provide an inherently less safe environment with

respect to electrical hazards. Individual connection of each piece of

equipment to fixed mains socket-outlets is the preferred means of

connection.

If multiple portable socket outlets are used, they are subject to the following

constraints:

• They shall not be placed on the floor.

• Additional multiple portable socket outlets or extension cords shall not be

connected to the system.

• They shall only be used for supplying power to equipment which is

intended to form part of the system.

PowerLab Owner’s Guide

10

Cleaning and Sterilization

ADInstruments products may be wiped down with a lint free cloth moistened

with industrial methylated spirit. Refer to the manufacturer’s guidelines or the

Data Card supplied with transducers and accessories for specific cleaning and

sterilizing instructions.

Preventative Inspection and

Maintenance

PowerLab systems and ADInstruments front-ends are all maintenance-free

and do not require periodic calibration or adjustment to ensure safe

operation. Internal diagnostic software performs system checks during power

up and will report errors if a significant problem is found. There is no need to

open the instrument for inspection or maintenance, and doing so within the

warranty period will void the warranty.

Your PowerLab system can be periodically checked for basic safety by using

an appropriate safety testing device. Tests such as earth leakage, earth bond,

insulation resistance, subject leakage and auxiliary currents and power cable

integrity can all be performed on the PowerLab system without having to

remove the covers. Follow the instructions for the testing device if performing

such tests.

If the PowerLab system is found not to comply with such testing you should

contact your PowerLab representative to arrange for the equipment to be

checked and serviced. Do not attempt to service the device yourself.

Environment

Electronic components are susceptible to corrosive substances and

atmospheres, and must be kept away from laboratory chemicals.

Storage Conditions

• Temperature in the range 0–40 °C

•Non-condensing humidity in the range 0–95%.

Operating Conditions

• Temperature in the range 5–35 °C

• Non-condensing humidity in the range 0–90%.

Disposal

• Forward to recycling center or return to manufacturer.

Chapter 1 Overview 11

You r PowerL a b ® recording unit, together with a range of specialized

application programs, provides a versatile data recording and analysis system

when used with a Windows or Macintosh computer. This chapter provides an

overview of the PowerLab system and describes the basic features, connectors

and indicators of the PowerLab.

Note that the software supplied with the PowerLab should be installed before

you connect the PowerLab to your computer.

1Overview

PowerLab Owner’s Guide

12

How to Use This Guide

This owner’s guide describes how to set up and begin using your PowerLab

recording unit. The chapters provide an overview of the PowerLab system (the

combined software and hardware package), and a more detailed look at the

features of your recording unit and its connection to your computer. The

appendices provide technical information about the recording unit and

solutions to problems. At the end of this guide is a glossary of hardware terms

and an index.

Software Installation

You should install ADInstruments application software before connecting or

using your PowerLab.

The Getting Started with LabTutor manual provides full installation

instructions for the LabTutor software.

The Getting Started with PowerLab manual provides full installation

instructions for the LabChart and Scope software.

PowerLab Check

Please do not attempt to connect the PowerLab to a power outlet or computer

or turn it on until you have checked it as described below.

1. Check that all items in the accompanying packing list are included in the

box.

2. Check that there are no obvious signs of external damage to the PowerLab.

3. Check that there are no obvious signs of internal damage, such as rattling.

Pick up the PowerLab, tilt it gently from side to side, and listen for

anything that appears to be loose.

If anything is missing, or the PowerLab seems to be damaged in any way,

contact your authorized ADInstruments representative immediately. Up-to-

date contact addresses are available from the ADInstruments website.

Connection information is in Chapter 2.

Chapter 1 Overview 13

The PowerLab

This section describes the connectors and indicators of the PowerLab 15T,

2/26, 4/26 and 26T.

The Front Panel

The front panel (Figure 1–1 to Figure 1–4) provides the connectors for

obtaining external signals, and indicators for various functions. This section

describes each of the front panel features:

• Power and Status indicator LEDs

• Trigger indicator LED and BNC connector (not on PowerLab 15T)

•Output BNC connectors

•Input DIN connectors

• Input BNC connectors (PowerLab 2/26 and 4/26 only)

For the PowerLab 15T and 26T:

• Isolated Stimulator switch, indicator LEDs and output connectors

•Bio Amp connector.

Indicators

The Power and Status indicators on the front panel should flash briefly while

the PowerLab is starting up. Under normal conditions, the Power indicator

should glow blue and stay lit. This simply shows that the PowerLab is getting

power.

The Status indicator should flash yellow and then stay green when the

PowerLab is switched on, and again when an ADInstruments application is

opened. It provides some visual indication of what the PowerLab is doing, and

will flash different patterns and colors depending on the state of the

PowerLab. See Table 2–1 for details.

Trigger

The external trigger connector of the PowerLab 2/26, 4/26 and 26T allows you

to use an external signal to synchronize recording to an external event. This

input can handle voltages of up to ±12 V. The threshold voltage (the voltage

above which the trigger circuit activates) is 2.0 volts for a rising edge. When

the trigger threshold is crossed, the indicator beside the external trigger

connector will glow yellow. The external trigger is described in more detail in

Appendix A, and the software documentation covers its practical use in

normal recording.

PowerLab Owner’s Guide

14

Analog output

connectors

Power and

Status

indicators

Bio Amp

connector

Analog input

connectors

Isolated Stimulator

connectors

Trigger indicator and connector

Analog input

connectors

Power and

Status

indicators

Analog output

connectors

Trigger indicator

and connector

Figure 1–1

The front panel of the

PowerLab 15T

Figure 1–2

The front panel of the

PowerLab 26T

Figure 1–3

The front panel of the

PowerLab 2/26

Figure 1–4

The front panel of the

PowerLab 4/26

Chapter 1 Overview 15

Analog Output

The PowerLab can generate a stimulus voltage through its analog output

sockets (marked Output + and –), giving positive, negative, differential, or

independent stimuli, depending on the sockets used and the software settings.

By default, the outputs are used for complementary (differential) stimulation,

where Output + is positive and Output – is negative.

When Output + is used, a positive stimulus voltage (set up in the software)

gives a positive voltage output, and a negative voltage a negative one. When

Output – is used, the voltage outputs are inverted. When both output sockets

are used, the stimulus is the difference between the voltages at the positive

and negative outputs: you could generate up to a 20-volt pulse, using a setting

of ±10 V.

You can use either the analog output or the isolated stimulator, but not both at

once.

Analog Inputs

The analog inputs can record external signals from ±10 V down to the

microvolt (μV) range, without the need for additional external amplification.

Each analog input has an independently programmable gain amplifier with its

own filtering. Note that applying more than ±15 V to the analog inputs can

damage the circuitry.

The PowerLab 15T and 2/26 have two independent analog inputs marked

Input 1 and 2; the PowerLab 26T and 4/26 have four such inputs marked 1–4.

These 8-pin DIN connectors and BNC connectors can be used as:

• Single-ended inputs, where the difference between the signal and ground

is recorded.

• Differential inputs, where the difference between the positive and negative

input signals is recorded.

•Pod connectors, which allow the connection of ADInstruments pods, or

those transducers designed for direct connection.

On the 15T and /26 model PowerLabs, the impedance between the earthing

stud (ground connection) and the input connector grounds is close to zero.

Note that with the PowerLab 26T:

• ADInstruments front-ends, such as the ML221 Bridge Amp, can be used

with inputs 1 and 2 (but not inputs 3 or 4) by connecting them with the

DIN-to-BNC adaptor.

• When an ADInstruments pod is connected to either input 3 or 4, the

corresponding Bio Amp input is turned off.

SWARNING

PowerLab inputs and

outputs are not electrically

isolated (except for the

Bio Amp input and the

Isolated Stimulator outputs)

and so should never be

connected to human

subjects.

PowerLab Owner’s Guide

16

Isolated Stimulator

The PowerLab 15T and 26T have a built-in, isolated, constant-current pulse

stimulator that can be used for any general-purpose stimulation with humans.

The Isolated Stimulator section of the front panel has two output sockets, two

indicator lights and a safety switch. Note that you cannot use the analog

output and the isolated stimulator at the same time.

The stimulus output is supplied via two 4 mm shrouded banana sockets; the

left-hand (red) socket is positive, the right-hand (black) socket is negative.

These are designed for use with shrouded male 4 mm plugs (the shrouding is

to prevent accidental stimulation while fitting or removing the plugs). The bar

stimulus electrode supplied with the PowerLab uses such plugs.

The output is capable of supplying 100 V pulses at currents up to 20 mA, so it

should be treated with caution. The Isolated Stimulator Pulse indicator is an

LED that indicates the current status of the Stimulator. It will flash green for

every stimulus pulse, and may seem to glow green constantly at higher

stimulus frequencies. The OOC (out-of-compliance) indicator is a yellow

LED. When lit, it indicates that the output is overloaded or out of compliance

(compliance is the ability to supply voltage to meet the required current). This

means that the impedance of the tissue being stimulated is too high, or there

is a poor electrical connection (possibly due to electrode drying), and that the

Isolated Stimulator can no longer supply constant current stimulation. If this

should happen, try reducing the output current amplitude, and check all

connections.

To provide an additional level of safety, a safety switch is located on the front

panel to allow the output to be switched on and off as needed. The switch

should be flicked down to turn the output off: doing so disconnects the output

sockets from the internal circuitry, allowing connections to be made safely

while the PowerLab is on.

The Bio Amp Inputs (Inputs 3 and 4)

The PowerLab 15T and 26T have a connector for two Bio Amp inputs,

marked Bio Amp Input 3 & 4. These biological amplifiers perform electrically

isolated measurements of biological signals, such as electrocardiograms

(ECG) and electromyograms (EMG). The two Bio Amp inputs have a

common six-pin connector with a shared ground signal and are internally

configured to use channels 3 and 4 of the PowerLab.

The PowerLab comes supplied with a 5-lead Bio Amp cable and lead wires.

The Bio Amp inputs should only be used with the supplied Bio Amp cable

and approved leads. Other cables may not meet safety requirements. Note:

with the PowerLab 26T, connecting an ADInstruments pod to either analog

input 3 or 4 turns off the corresponding Bio Amp input.

Chapter 1 Overview 17

The Back Panel

The back panels of the PowerLab (Figure 1–5 to Figure 1–7) provide the

sockets to connect the PowerLab to the computer, other devices and the

power outlet. This section describes each of the back panel features:

• Audio connector (PowerLab 26T only)

•I

2C connector (not on PowerLab 15T)

•USB connector

• Digital input and output connectors (PowerLab 26T only)

•Ground connector

• Power switch and socket.

Device rating

information

USB connector Ground Device rating

information

Power switch

and socket

Digital Input

connector

I2C connector

Audio connector

USB connector Power switch

and socket

Ground

Digital Output

connector

Figure 1–5

The back panel of the

PowerLab 15T

Figure 1–6

The back panel of the

PowerLab 26T

Figure 1–7

The back panel of the

PowerLab 2/26 and 4/26

PowerLab Owner’s Guide

18

Audio Connector

The PowerLab 26T has an audio output to monitor the Bio Amp channels. It

provides stereo sound (using signals from Inputs 3 and 4). The 3.5 mm stereo

socket can be used with a wide range of headphones or externally powered

speakers. The audio output is particularly helpful when monitoring nerve

firings, to assist in the placement of electrodes, for instance.

I2C Connector

The I2C output port (not on PowerLab 15T) provides power and control

signals for front-ends manufactured by ADInstruments.

Many front-ends can be daisy-chained together and connected through the

I2C ports, so long as there are enough analog inputs on the PowerLab. A

maximum current of 50 mA can be provided through this bus, so it should

not be used for third-party devices that require more current than that.

USB Connector

The PowerLab connects to your computer using a USB 2.0 connector and

cable, therefore your computer must have USB connectors or a PCI USB card

to receive data from the PowerLab.

You can safely disconnect or reconnect a USB-connected PowerLab while the

computer remains on. However, ADinstruments software (LabTutor,

LabChart or Scope) should not be running while you do this. Read the details

on USB in Appendix A of this guide before connecting your PowerLab to your

computer.

Digital Input and Output Connectors

The digital input and output ports (PowerLab 26T only) let you monitor and

control external devices, respectively, with the PowerLab.

The digital input monitors state changes: you can have a predefined comment

automatically inserted during recording when a digital input changes to a

particular state. The eight lines of the connector allow monitoring of up to

eight devices. The digital output can turn on and off external devices, for

example pumps, relays, and indicator lights, or can signal to some other

device. The eight lines of the connector allow control of up to eight devices.

Technical details of the digital input and output connectors are given in

Appendix A. Note that any cables connected to either the digital input or

output must be less than 3 m in length in order to maintain EMC compliance.

More information on the use of digital inputs and outputs is given in the Help

for the software.

Chapter 1 Overview 19

Ground Connector

A special earthing (grounding) stud is provided on the rear panel of the

PowerLab. This is an equipotential bonding connection post compatible with

the DIN 42801 standard. The earthing stud is directly connected to the earth

pin of the power socket and the PowerLab chassis. It is used as a primary

earth connection (equipotential connection point) in situations that require

this type of connection, or if there is no ground provided via the power cord.

Safety standards in laboratories and similar environments may require

additional grounding protection when connecting equipment to human

subjects, and their relevant standards or guidelines should be observed.

Power Connector

The power switch on the back right of the PowerLab turns the PowerLab on

and off; the 3-pin IEC power socket is used to connect your PowerLab to a

power cable. The power supply is universal, and can use all common

international mains power supplies (100–240 V AC, 50/60 Hz).

The PowerLabs are not fitted with replaceable fuses. The power supply is

short-circuit protected, and should not damage the internal fuses unless a

major fault develops. If that happens, the unit must be returned for service by

qualified service personnel. Do not attempt to replace internal power supply

fuses yourself. For further assistance please contact your nearest

ADInstruments representative.

The Bio Amp Cable

Connections are made to the Bio Amp inputs using the supplied Bio Amp

cable and leads. The cable plugs into the six-pin input socket on the front

panel: a notch in the plug ensures that polarity is correct. Only the supplied

Bio Amp cable and leads should be used. Other cables may not meet safety

requirements. The PowerLab 26T and 15T are supplied with a 5-lead Bio Amp

cable and lead wires; it uses a shared ground signal for its Bio Amp channels.

The cable is of the sort often used for ECG or EMG work, a Tronomed D-

1540 cable, and has a cable yoke with five sockets for the leads.

The supplied leads click into place in the cable yoke, and have snap

connectors at the other end to connect to typical ECG electrodes. The leads

are color-coded for ease of identification.

ADInstruments supplies other types of lead wires that connect to the Bio

Amp cable yoke, such as EEG Flat Electrodes and dry earth straps. Also

available are disposable and reusable electrodes, electrode cream (for reusable

PowerLab Owner’s Guide

20

electrodes), electrode paste, and abrasive gel for lightly abrading the skin

before the electrodes are attached.

Other ADInstruments Hardware

ADInstruments has a range of optional devices that can be connected to your

PowerLab. They extend the types of experiments you can conduct and the

data you can record, and include:

• Pods — small, low-cost signal conditioners for specific tasks, for use with

precalibrated transducers, and which are automatically recognized by the

PowerLab and application software.

• Front-ends — advanced signal conditioners which are automatically

recognized by the PowerLab and software, and which provide specialized

data acquisition features (not used with the PowerLab 15T).

• Transducers — either for use with a specific pod, or which plug directly

into the PowerLab, depending on their type.

A PowerLab can usually have as many pods or transducers connected to it as

it has appropriate connectors. All are easily transferred between PowerLabs.

Full information on such hardware is available from your local

ADInstruments representative or from the ADInstruments website.

To Bio Amp inputTo electrodes

Figure 1–8

The Bio Amp cable yoke,

with 5 leads attached

Chapter 2 Setting Up 21

This chapter describes:

• The PowerLab’s internal self-test.

• The USB connection between the PowerLab and the computer.

• The software features specific to the built-in Isolated Stimulator and Bio

Amp.

2Setting Up

PowerLab Owner’s Guide

22

The PowerLab Self-test

The PowerLab performs a diagnostic self-test each time it is switched on.

Before connecting it to the computer for the first time, you should test that

your PowerLab is functioning properly, as follows:

1. Connect the PowerLab to a power outlet using the power cable that came

with your unit. Turn on the power at the wall.

2. Turn on the power switch located on the rear of the unit, and observe the

Power and Status indicators on the front panel while the PowerLab is

starting up:

• The Power indicator should glow blue while the PowerLab is on.

•The Status indicator should flash yellow and then stay green.

If the Status indicator stays green, the internal diagnostic check has completed

successfully. The PowerLab can now be switched off and connected to the

computer.

If the Power indicator does not glow blue when the power switch is turned on,

then there is a problem with the power source, power cable or PowerLab itself.

Check the connections and cables.

If the Status indicator is flashing red, then the PowerLab has detected an error

during the self-test. Restarting the PowerLab should clear a temporary

problem.

If the PowerLab does not seem to be getting power, or the Status indicator

flashes red, even after restarting, refer to the ADInstruments website

(www.adinstruments.com/support/tsupport/education) or contact your

authorized ADInstruments representative. Do not attempt to repair the

PowerLab yourself.

Status Indicator Meaning

Off Idle and not yet initialized by the software.

Green Idle, initialized, and waiting for a command from the computer.

Yellow Sampling, or communicating with the computer.

Four red flashes

then one yellow

The PowerLab has detected a low-level software or hardware

fault. It will repeat until the PowerLab is turned off.

Red flashes The PowerLab has detected an internal fault during the

power-up test. It will repeat until the PowerLab is turned off.

Table 2–1

Status indicator codes

Chapter 2 Setting Up 23

Connecting the PowerLab

Use the USB cable supplied with your PowerLab to connect the USB port on

the back panel to the USB port on the computer, or to an active USB hub

connected to the computer (see Figure 2–2). USB ports and cables should be

marked with a trident-like icon (Figure 2–1). Further detail about USB

connections is provided on page 41 of Appendix A.

ADInstruments Software

The integration of hardware and software in the PowerLab system allows all

hardware functions, including those of any connected signal conditioners, to

be controlled from within the software.

LabTutor Software

When the PowerLab is used with the LabTutor application, the LabTutor

experiments have pre-configured settings for the PowerLab, and for any signal

conditioners needed for the experiment. For more information about the

LabTutor application please refer to LabTutor 4 Suite Administrator’s Guide.

LabChart Software

When the PowerLab is used with the LabChart (or Scope) application, the

PowerLab functions are set up from within that software. The software

controls for most functions, such as sampling speed, are described in the

Figure 2–1

USB Icon

USB icon

Computer or hub

connection

PowerLab

USB cable

Figure 2–2

Connecting a PowerLab to

a computer with USB

PowerLab Owner’s Guide

24

documentation for LabChart (or Scope). For more information about the

LabChart application please refer to the LabChart Help.

The software controls specific to the signal conditioners built into the

PowerLab 26T and 15T (an Isolated Stimulator and two Bio Amps) are

described below.

The Isolated Stimulator

The PowerLab 26T and 15T have both normal and isolated outputs, and you

can switch between them in software. The Isolated Stimulator provides

software-controlled, isolated, constant-current pulse stimuli that can be used

with human subjects. The stimulis is produced at the outputs on the front

panel of the Stimulus Isolator. The stimulus is independent of the PowerLab

sampling rate and can be generated whether the PowerLab is sampling or not.

The stimulus is set up using the Stimulator dialog.

Choose Setup > Stimulator.... to display the Stimulator dialog (Figure 2–3).

This dialog is named Stimulus Isolator on the Macintosh (Figure 2–4). When

setting up the Stimulus Isolator, you:

• Choose how stimulation should start.

• Choose a preconfigured stimulus type or mode.

• Optionally, on Windows, create a custom stimulus waveform.

• Set stimulus parameters, such as start delay, pulse width and current

amplitude.

Scope has a different Stimulator dialog to that of LabChart: in the Stimulator

dialog you can choose Pulse and Multiple in the Mode pop-up menu (to

produce single or multiple pulses, respectively).

Note that if you connect a Stimulus Isolator front-end to a PowerLab 15T or

26/T, only the external stimulator is used.

Choosing How Stimulation Should Start

Stimulation can be set to start in different ways:

•When sampling starts: stimulation begins automatically when the

LabChart Start button is clicked, and continues until sampling stops. Use

the On and Off buttons to control pulse delivery, if necessary.

•Manually: stimulation begins when Stimulate in the dialog is clicked, and

continues until sampling stops. Use the On and Off buttons to control

pulse delivery, if necessary.

•Independently of sampling: stimulation begins when On in the dialog is

clicked, whether or not LabChart is sampling. Available in LabChart for

Windows only.

Chapter 2 Setting Up 25

In all three modes, you can immediately restart a stimulus waveform by

clicking Stimulate.

Set stimulus

parameters

Specify a custom

stimulus

waveform

Choose a stimulus

type preset

Choose how stimulation should start

Configure the

range of valid

parameter values

in the Parameter

Settings dialog

Set the number

of pulses to be

delivered

Mark the stimulus

event in a channel

Turn stimulation on

(Pulse) or off

Click to start a

train of pulses

(when sampling

and manual start

is selected)

Change the stimulus frequency range

Check to set the

interval between

pulse starts

Figure 2–3

The Stimulator dialog,

Windows

Figure 2–4

The Stimulus Isolator

dialog, Macintosh

PowerLab Owner’s Guide

26

Choosing a Stimulus Type

The Stimulator only offers the Isolated Pulse stimulation mode (Pulse on

Macintosh). This generates a rectangular pulse stimulus that starts at zero

current, is raised to the set current amplitude for the set pulse width

(duration), and then falls to zero current again. By default, the stimulator is

off and the current amplitude is set to zero.

Creating a Custom Stimulus Waveform

In LabChart for Windows, you can:

• Specify whether parameter controls are displayed in the Stimulator and

Stimulator Panel dialogs.

• Define a sequence of segments to create a custom stimulus waveform.

Click Custom... to display the Waveform Customization dialog. Further

details about using this dialog are available in the LabChart Help.

Setting Stimulus Parameters

You use the text boxes and sliders to set values for the stimulus parameters. In

LabChart for Windows, you can use the Settings dialog for each parameter to

configure the range of values available to the parameter text box and slider

controls. Using suitable values can improve the precision of control over the

stimulus parameter when using the slider and spinner controls.

Windows

In LabChart for Windows, the following stimulus parameters can be set:

Start Delay: the wait time before stimulation is delivered, once the stimulus

waveform has been started.

Repeats: the number of times the stimulus waveform is repeated, once

started.

Max Repeat Rate: the maximum frequency with which the stimulus

waveform is repeated (either 0.1—20 Hz or 6—1200 /min), or the interval

between each pulse start (0.05—10 s).

Pulse Width: the duration of each pulse. The pulse duration is restricted to the

range from 50 μs to 200 μs for safety reasons.

Current: the amplitude of the stimulus current (0 to 20 mA).

End Delay: the wait time at the end of a stimulus segment, after which the

next segment is delivered. This is not the same as a Delay segment.

Macintosh

In LabChart for Macintosh, the following stimulus parameters can be set:

Chapter 2 Setting Up 27

Range: lets you select the range for the Frequency control; either 0.1—2 Hz,

0.1—20 Hz, or 2—200 PPM (~0.033 Hz to ~3.3 Hz). PPM (pulses per minute)

can sometimes be a more convenient expression of the pulse frequency.

Frequency: the rate at which pulses are delivered; available values are within

those set with Range.

Pulse duration: the time for which the pulse lasts, from 50 μs to 200 μs

(0.05 ms to 0.2 ms). The pulse duration is limited to 200 μs for safety reasons.

Amplitude: the exact amplitude of the stimulus current, from 0 to 20 mA.

Marker Channel

If you choose a channel from the Marker Channel pop-up menu, then the

start time of a stimulus pulse is marked by a small data spike (this adds to any

data in that channel).

The Stimulator Panel

Once you have set up stimulation using the Stimulator dialog, you can easily

start or stop stimulation or change settings while sampling, by using the

Stimulator Panel. Choose Stimulator Panel from the Setup menu to open it

(Stimulus Isolator Panel on Macintosh).

On Windows, you can specify which parameter controls are displayed in the

panel using checkboxes in the Panel column of the Waveform Customization

dialog. See the LabChart Help for details.

The Stimulator Panel ‘floats’ in front of the active window, can be moved

around with its title bar, and can only be dismissed by clicking its close box.

Figure 2–5

The Stimulator Panel

Windows (upper)

Macintosh (lower): manual

control of stimuli

This button appears when

manual stimulation is selected

PowerLab Owner’s Guide

28

The Bio Amp

The PowerLab 26T and 15T have two-channel Bio Amps, which are internally

configured to use channels 3 and 4. The Bio Amp dialog allows software

control of the combined input amplifiers and filters in the PowerLab and Bio

Amps. The signal present at a channel’s input is displayed so that you can see

the effects of changes straight away. Once settings in the dialog are changed,

click OK to apply them.

The Bio Amp dialog appears when you choose Bio Amp… from a Channel

Function pop-up menu (or click Bio Amp… in the Input Settings column in

the Channel Settings dialog). To set up many channels quickly, click the

arrows by the dialog title, or press the right or left arrow keys on the

keyboard, to move to the equivalent dialogs for adjacent channels. This skips

channels that are turned off. The channel number is shown next to the arrows,

and the channel title

(if any) is shown in the vertical Amplitude axis of the dialog.

Signal Display

The input signal is displayed so you can see the effect of changing the settings

— no data is recorded while the Bio Amp dialog is open. Slowly changing

waveforms will be represented quite accurately, whereas rapidly changing

signals will be displayed as a solid dark area showing only the envelope

(shape) of the signal formed by the minimum and maximum recorded values.

The average signal value is shown at the top left of the display area.

You can stop the signal scrolling by clicking the Pause button at the bottom

left (Macintosh) or top right (Windows) of the data display area. This changes

to the Scroll button on the Macintosh. Click the Scroll button to start scrolling

again.

Shift and stretch the vertical Amplitude axis, by clicking and dragging it in

various ways, to make the best use of the available display area.

It functions the same as the Amplitude axis of the Chart Window, controls are

identical and any change is applied to the Chart Window.

Setting the Range

The Range pop-up menu lets you select the input range, or sensitivity, of the

channel — the combined range of the PowerLab and Bio Amp. Changing the

range in the Bio Amp dialog is equivalent to changing it in the Chart window.

The default setting (if you have not loaded a settings file) is 20 mV, rather

than 10 V, and the ranges go down to 100 μV in eight steps.

Chapter 2 Setting Up 29

Filtering

Each of the Bio Amps in the PowerLab has low-pass, high-pass and mains-

filter circuitry that can be adjusted to suit the recording. Note: the settings for

one filter type may restrict the possible settings for the other.

High-pass filtering

The High pass pop-up menu gives the choice of two high-pass filters: 0.5 and

Range pop-up

menu

Signal amplitude

Pause/Scroll button

Filtering

options

Amplitude axis

Pause and Scroll buttons

Open the Units

Conversion dialog

Compression

buttons

Amplitude axis Signal amplitude

Click this to open the Units Conversion dialog

Filtering

options

Range pop-up

menu

Figure 2–6

The Bio Amp dialog for

Macintosh

Figure 2–7

The Bio Amp dialog for

Windows

PowerLab Owner’s Guide

30

10 Hz. The high-pass filter allows high frequencies in the signal to pass, and

removes frequency components below the filter frequency (including any DC

signal). These filters are useful for removing slowly moving baselines, such as

motion or respiration artifacts, particularly in ECG (EKG) recordings.

Low-pass filtering

The Low pass pop-up menu gives the choice of eight low-pass filters: 10, 20,

50, 100, 200 and 500 Hz, and 1 and 2 kHz. These filters are useful for

removing high-frequency signals, such as noise.

DC Restore

Click DC Restore to reduce the time constant of the high-pass filter so that

the filter can rapidly adjust to an altered baseline value.

Mains filter

The mains filter allows you to remove interference at the mains frequency

(typically 50 or 60 Hz). Select Mains filter to turn on the mains filter. This is

an adaptive filter and should only be used when the signal to mains noise

ratio is less than 36 dB, that is the mains noise amplitude is greater than 1/64

of the signal amplitude. More details on the mains filter can be found in the

LabChart Help Center.

Anti-alias

Select Anti-alias to apply a sample rate-dependent low-pass filter that prevents

aliasing artifacts. The input signal is sampled and digitized at 100 kHz. The

AD converter is preceded by an analog anti-aliasing (low-pass) filter of fixed

cutoff frequency (Ý49 kHz). When LabChart or Scope samples at 100 kHz,

the converted samples are passed on unchanged. At all other LabChart or

Scope sampling rates, an additional (digital) filter is optionally applied to the

AD converter's 100 kHz output stream. This is a decimating FIR filter whose

cutoff frequency is set to the Nyquist value: half the LabChart or Scope

sampling frequency. It thus acts as an automatic anti-aliasing filter, providing

optimum noise rejection in the recorded data. Attenuation in the stop band is

at least 40 dB. Note that anti-aliasing is disabled at sampling rates below 100

Hz so as to prevent the delay that otherwise occurs as samples pass through

the FIR filters.

The anti-aliasing filter characteristics are chosen to give the fastest step

response without overshoot (corresponding to an analog Bessel filter). Such a

response is suited to most types of physiological recordings. In the frequency

domain, the filter response starts to roll off well below the cutoff frequency. In

certain (relatively uncommon) types of measurement, a maximally flat

response is desirable; this can be obtained by turning anti-aliasing off.

Chapter 2 Setting Up 31

Inverting the Signal

Selecting Invert allows you to invert the signal on the screen. It provides a

simple way to change the polarity of the recorded signal without having to

swap the connections to the recording electrodes.

Units

Clicking Units… opens the Units Conversion dialog, letting you specify the

units for a channel, and, using waveform measurements, to calibrate the

channel. A waveform in the data display area of the Bio Amp dialog is

transferred to the data display area of the Units Conversion dialog. (Use the

Pause button to capture a specific signal.) The units conversion only applies to

subsequently recorded signals, so it is more limited than choosing units

conversion directly from the Channel Function pop-up menu, as it does not

allow conversion of individual blocks of data.

PowerLab Owner’s Guide

32

A

APPENDIX

Appendix A Technical Aspects 33

This appendix describes some of the important technical aspects of your

PowerLab, to give some insight into how they work. You do not need to know

the material here to use your PowerLab. It is likely to be of special interest to

the technically minded, indicating what the PowerLab can and cannot do, and

its suitability for particular purposes. You should not use it as a service

manual: user modification of the PowerLab voids your rights under warranty.

A Technical

Aspects

PowerLab Owner’s Guide

34

How it Works

The PowerLab is essentially a smart peripheral device specifically designed to

perform the various functions needed for data acquisition, signal

conditioning, and pre-processing. It contains its own microprocessor,

memory and specialized analog amplifiers for signal conditioning.

All sampling, output and communication functions are controlled by an

internal microprocessor. This microprocessor has access to 16 MB of internal

dynamic RAM for data storage and buffering. The PowerLab uses USB 2.0 to

communicate with the computer, if the computer is USB 2.0 compliant. This

provides data transfer rates of up to 480 Mbits per second. If the computer

only supports USB 1.1 the data transfer rate will be slower.

The 15T and 2/26 PowerLabs have two analog inputs, whereas the 26T and

4/26 PowerLabs have four analog inputs. They are used to record external

signals prior to digitizing. Each of these input amplifiers connects to a

separate 16-bit ADC (analog-to-digital converter) that samples at 100 000

samples per second. The sampling process is handled independently of the

processor core through a sampling control engine using direct memory

access. The CPU assembles groups of samples into blocks and then transmits

them to the computer, where the software receives, records and displays the

data.

Two 16-bit DACs (digital-to-analog converter) are used to provide an analog

output or stimulation capability through the analog outputs of the PowerLab

(marked ‘Output’ on the front panel). The DACs can produce constant DC

voltage levels or waveforms under software control. Stimulation frequency is

completely independent of the analog input sampling rate. The output of the

DACs is fed through a programmable attenuation network to produce

different output ranges. The signal is then split into a positive and negative

output through buffer amplifiers. The outputs are capable of driving up to

20 mA into a load.

The PowerLab uses an IEC60601-1 (medically) compliant switching power

supply. This provides a universal input that handles all common international

voltage supplies and frequencies without the need to change voltage ranges.

This power supply is also internally protected in the case of a problem. It is

important to note that the PowerLab has a limited amount of power available

for external devices. Because of these power limitations, you should not use

the PowerLab as a power source for external devices other than those

produced by ADInstruments.

Appendix A Technical Aspects 35

The Analog Inputs

PowerLab input amplifiers have been designed with a considerable amount of

computer-controlled gain (up to × 2000). Thus it is possible to record a variety

of signals without any external pre-amplification. Each analog input is a

separate DC amplifier with programmable gain able to be set independently

(the gain is set through the software range control). The PowerLab inputs can

be set by the software to be either single-ended or differential. In the

differential setting, the amplifier measures the difference between the positive

and negative inputs, irrespective of ground.

It is important to note that the PowerLab grounds the inputs to amplifiers not

in use. It also grounds each amplifier and measures the DC offset voltage

when the gain is changed. In this way, the software corrects for any DC drift

or offset in the circuits that may develop over time or between readings.

Input impedance is one megohm (1 MΩ). Each analog input is fitted with a

fixed 25 kHz low-pass filter.

On the 15T and /26 model PowerLabs, the impedance between the earthing

stud (ground connection) and the input connector grounds is close to zero.

The Analog Outputs

The analog outputs provide computer-controlled variable outputs (±10þV)

that can be used with the LabChart and Scope applications either directly as a

stimulator, or to control peripheral devices. All stimulation voltage is

generated by the PowerLab via the output sockets on the front of the

PowerLab (marked Output + and –), giving positive, negative, differential, or

independent stimuli, depending on the sockets used and the software settings.

By default, the outputs are used for complementary (differential) stimulation,

where Output + is positive and Output – is negative. When Output + is used,

a positive stimulus voltage (set up in LabChart or Scope) gives a positive

voltage output, and a negative voltage a negative one. When Output – is used,

the voltage outputs are inverted. When both output sockets are used, the

stimulus is the difference between the voltages at the positive and negative

outputs: you could generate up to a 20-volt pulse, given a ±10 V range setting.

SCaution

Applying more than ±15 V to

the input can damage the

input circuits.

SWarning

Analog outputs are not to

be used for connection to

human subjects.

Ground

From DAC +

–

+10 V

– 10 V

+10 V

– 10 V

Figure A–1

The analog output stage,

set up for a differential

stimulus

PowerLab Owner’s Guide

36

The External Trigger

The external trigger input (not on PowerLab 15T) is marked ‘Trigger’ on the

front panel and provides a digital input for synchronizing sampling with

external devices. It allows either a voltage level or a contact closure to trigger

recording. Note that for either mode the trigger signal must be present for at

least 3 μs to register as an event. When a trigger event occurs, the indicator

light will glow yellow.

When set up through software to use a voltage level, above which a rising edge

trigger event is registered, the external trigger level is 2 V. The external trigger

input is off for input voltages between –12 V and the external trigger level,

and on between that level and +12 V. The input will be overloaded if the

voltage is outside the range –12 V to +12 V. The trigger input is isolated when

set up for a voltage level.

The equivalent circuit of the external trigger has two diode protection.In the

external contact closure mode, the trigger input will respond to a direct short

between the center pin and outer ring of the BNC. This can be achieved with

an external relay contact, a manual push-button or a microswitch. The trigger

input is not electrically isolated when set up for contact closure.

The equivalent circuit for the external closure trigger is shown in Figure A–3.

The BNC input connects to a TTL circuit via a resistor circuit and has two-

diode protection.

+3.3 V

Trigger

(BNC connector) 1.2k ohm

resistor

47k ohm

resistor

100 pF

Figure A–2

The equivalent circuit of

the external trigger input,

when set up for a voltage

level

+3.3 V

Trigger

(BNC connector) 1.2k ohm

resistor

47k ohm

resistor

100 pF

Figure A–3

The equivalent circuit of

the external trigger input,

when set up for contact

closure

Appendix A Technical Aspects 37

In order for the external trigger to work, a voltage must be applied between

the outer ring and the inner pin of the connector. Applying a voltage just to

the center pin may not work.

Bio Amp Input (Inputs 3 & 4)

The PowerLab 15T and 26T have one common connector for two Bio Amp

channels, marked Bio Amp 3 & 4. These two independently controllable,

electrically isolated, biological amplifiers are suitable for a range of basic

physiological measurements. The two Bio Amp inputs are internally

configured to use channels 3 and 4 of the PowerLab. The Bio Amps have a

common six-pin connector with a shared ground.

Each amplifier consists of an electrically isolated, AC coupled, differential

amplifier with programmable gain able to be set independently (the gain is set

through the software range control: the less the range, the more the gain). The

gain is controlled by optically isolated digital control signals from the non-

isolated section. The signal is then applied to an isolation amplifier which

provides electrical isolation of the input stage from the supply.

The non-isolated stage consists of a series of filters and amplifiers. The first

part of the stage is a high-pass filter designed to remove any DC components

from the signal and the isolated stage. This is followed by amplification and an

active notch filter. The notch can be turned on or off under software control

as needed. The frequency of the notch filter is automatically set to either 50 or

60 Hz to match the frequency of the connected power supply.

The low-pass filter is an eighth-order, switched-capacitance, Bessel-type filter,

with a software-selectable range of frequencies. The output of the biological

amplifier is then passed to the standard PowerLab input amplifier circuit. On

the PowerLab 26T an amplifier connected to the output of the biological

amplifier is used to provide an audio output facility that can be used with

headphones or powered speakers.

IGND

IGND

IGND

Isolation amplifier

Output

Audio Output (26T only)

Gain control

HPF control

HPF

Auto

restore

Signal

Input

Reference

+

-

Isolation barrier

Figure A–4

Block diagram for one of

the two Bio Amplifiers

(Input 3 & 4)

PowerLab Owner’s Guide

38

The Isolated Stimulator Output

The Isolated Stimulator output provides a software-controlled, isolated,

constant-current pulse stimulator that can be used for any general purpose

stimulation.

The output stage consists of a high-voltage, constant-current source that can

produce pulses of variable duration and amplitude under full software control.

The current source can deliver pulses up to 20 mA at 100 V maximum

compliance levels; its amplitude is controlled by optically isolated digital

control signals from the non-isolated section. The output to the subject is

through high-isolation optical couplers.

Software and hardware safety features limit the energy delivered by the pulses

to within international safety standards. The pulse duration of the stimulator

can be set from 50 μs to 200 μs, and the pulse frequency can be adjusted

between 1 pulse per minute and 20 pulses per second on Windows (and

between 2 pulse per minute and 20 pulses per second on Macintosh).

The Isolated Stimulator Pulse indicator is an LED that is used to indicate the

current status of the Stimulator. It will flash green forevery stimulus pulse, and

may seem to glow green constantly at higher stimulus frequencies. The OOC

(out-of-compliance) indicator is a yellow LED. When lit, it indicates that the

output is overloaded or out of compliance (compliance is the ability to supply

voltage to meet the required current). This means that the impedance of the

tissue being stimulated is too high, or there is a poor electrical connection

(possibly due to electrode drying), and that the Isolated Stimulator can no

longer supply constant current stimulation. If this should happen, try

reducing the output current amplitude, and check all connections.

Isolation amplifier

Stimulate

Stimulus Output

Out of Compliance

Stimulator pulse

safety control

Stimulate

Current setting DAC

Stimulus Isolator

switch

INDICATORS

Constant current source

Stimulator

Power

Supply

Transformer

driver

Figure A–5

Block diagram of the

Isolated Stimulator

Appendix A Technical Aspects 39

PowerLab Accuracy

The PowerLab was calibrated at the factory to an accuracy of better than 0.1%.

Some ‘zero drift’ or ‘gain drift’ can occur with time. This can affect the

accuracy of measurements, especially at the highest input gains. The unit can

be recalibrated, but in most circumstances this is not necessary in its lifetime.

Calibration facilities. It is good practice to calibrate a measuring system from

the transducer to the output. After applying two known values to a transducer

(say at 20% and 80% of full scale) and recording the signal, you can use the

units conversion feature of ADInstruments software to convert and display

transducer readings in the appropriate units. This will compensate for any

minor inaccuracies in amplifier gain and transducer calibration.

DC drift compensation. When a recording is started manually or by

triggering, or the gain is changed, the input signal to the amplifier is grounded

and any DC, due to amplifier drift of temperature and age, is measured. The

measured voltage is removed from the input signal through software

correction, in a process transparent to the user.

Connectors

This section of the appendix contains ‘pinout’ and electrical details of some of

the connectors fitted to the PowerLab. You should read it carefully before

attempting to connect cables other than those supplied with the unit to the

PowerLab. Using cables that are wired incorrectly can cause internal damage

to the PowerLab and will void your rights under warranty. For further

information or advice please contact your nearest ADInstruments

representative.

Digital Input and Output

The digital input port and digital output port are 15-pin connectors situated

on the back panel of the PowerLab 26T. The eight digital input lines respond

to 3.3 V logic signals with a threshold of 1.2 V, and have a 10 kΩ input

impedance. The eight digital output lines can turn on and off, or signal to, up

to eight external TTL devices. The digital output lines are capable of driving

8mA each.

The inputs and outputs conform to industry standard HCMOS structures

powered with a 5 V supply. The digital input and output ports both have a pin

which can supply power to solid-state relays or similar devices. Total

PowerLab Owner’s Guide

40

aggregate current from these pins is 200 mA continuous at 5 V. The digital

input signals should not exceed 5 V.

Note that any cables connected to either the digital input or output must be

less than 3 m in length in order to maintain EMC compliance.

I2C Expansion Connector

The I2C port on the back panel of the PowerLab 2/26, 4/26 and 26T provides

expansion support for ADInstruments front-ends. This port provides both

power and control signals for these front-ends. The I2C bus has a daisy-chain

structure that allows simple connection of additional front-ends to the system.

A PowerLab can have as many front-ends connected to it as it has appropriate

connections. You should not attempt to run other external devices from the

I2C port: it is designed for use only with ADInstruments front-ends. Only

50 mA maximum current can be provided through this bus, so it should not

be used for third-party devices as they may draw more current.

Digital output

81

915

IN 2

IN 3

IN 1

IN 5

IN 4

IN 6

IN 7

IN 8

OUT 2

OUT 3

OUT 1

OUT 5

OUT 4

OUT 6

OUT 7

OUT 8

GROUND

5 V

18

15 9

GROUND

5 V

Digital input

Figure A–6

The pin assignments for

the digital input and output

connectors

15

96

DGND

UNREG–15 V

UNREG+7 V

UNREG+15 V

Front-end power

SCL

DSC

SDA

DSD

INT

I2C control signals

Figure A–7

The pin assignments for the

I2C connector

Appendix A Technical Aspects 41

Input Connectors

The input connectors (Figure A–8) of the PowerLab 15T, 2/26, 4/26 and 26T

are 8-pin DIN connectors. They allow the connection of ADInstruments pods

— small, low-cost signal conditioners for specific tasks, for use with

precalibrated transducers. Transducers designed for direct connection can be

provided with power and control through the connectors.

The PowerLab 2/26 and 4/26 also have BNC input connectors as well as the 8-

pin DIN connectors.

Note that with the PowerLab 26T:

• ADInstruments front-ends, such as the ML221 Bridge Amp, can be used

with inputs 1 and 2 (but not inputs 3 or 4) by connecting them with the

DIN-to-BNC adaptor.

• When an ADInstruments pod is connected to either input 3 or 4, the

corresponding Bio Amp input is turned off.

USB Connection

PowerLabs have a USB 2.0 port, and connect to a computer with USB ports or

a PCI USB card installed, allowing high data transfer rates to USB 2.0-

compliant computers (slower transfer to USB 1.1-compliant computers).

The signal must be transmitted in a certain time; in practical terms this means

cables between any USB devices, including hubs, must be no more than

5 meters (16 feet) in length, and with hubs in the chain, devices must be no

more than 30 meters (98 feet) from the computer. For proper use and reliable

results, the PowerLab needs a high-speed connection. Your PowerLab is

supplied with a high-speed USB cable. If you replace the USB cable, buy a

high-speed cable (fully shielded, twisted-pair and standard USB connections:

Figure A–8

The pin assignments for the

analog inputs

[4] Negative 5 V

[1] Positive 5 V

[6] Input (+) ref.

[2] Input (–)

[3] Input (+)

[5] SDA

[7] Analog ground

[*] Digital ground (metal ring)

[8] SCL

Figure A–9

The USB icon and port

PowerLab Owner’s Guide

42

a narrow rectangular plug at one end and a square plug with a bevelled top at

the other).

When devices that transfer a lot of information, such as scanners and video

cameras, are connected to the same USB tree and are used at the same time as

a PowerLab, sampling rates may be limited considerably (in LabChart) or

delay times between sweeps may increase (in Scope). Newer computers (both

PC and Macintosh) usually have several independent USB ports. Using these,

rather than a hub, to connect multiple devices will avoid them competing for

capacity (bandwidth).

You can safely turn on or off, or disconnect or reconnect, a USB-connected

PowerLab while the computer remains on, as long as the application program

(LabChart or Scope) is off when you do it.

Earthing and Ground Loop Noise

The prime function of earthing is safety, that is, protection against fatal

electrocution. Safety concerns should always override concerns about signal

quality. Secondary functions of earthing are to provide a reference potential

for the electrical equipment and to mitigate against interference.

The earthing (grounding) stud provided on the back panel of the PowerLab is

a potential equalization post and is compatible with the DIN 42801 standard.

It is directly connected to the earth pin of the power socket and the PowerLab

chassis. The earthing stud can be used where other electronic equipment is

connected to the PowerLab, and where conductive shields are used to reduce

radiative electrical pick-up. Connection to the stud provides a common earth

for all linked devices and shields, to reduce ground-loops.

The earthing stud can also be used where a suitable ground connection is not

provided with the mains supply by connecting the stud to an earthed metal

infra-structure, such as a metal stake driven into the ground, or metal water

piping. This may also be required in laboratories where safety standards

require additional grounding protection when equipment is connected to

human subjects. Always observe the relevant safety standards and

instructions.

Note that magnetically-induced interference in the recorded signal can be

reduced by minimizing the loop area of signal cables, for example by twisting

them together, or by moving power supplies away from sensitive equipment.

This can reduce the inductive pick-up of mains frequency fields. Please

consult a good text for further discussion of noise reduction.

Appendix B Specifications 43

B

APPENDIX

Analog Inputs

Number of input channels: 15T: 2 DIN

2/26: 2 DIN and BNC

4/26: 4 DIN and BNC

26T: 4 DIN

Configuration: DIN are single-ended or differential

BNC are single-ended

Amplification ranges: Range Resolution

±10 V 313 μV

±5 V 156 μV

±2 V 62 μV

±1 V 31 μV

±500 mV 15 μV

±200 mV 6 μV

±100 mV 3 μV

±50 mV 1.5 μV

±20 mV 625 nV

Maximum input over-voltage: ±15 V

Input impedance: 15T: 1 pF

2/26: 1 pF

26T: 1 pF (Inputs 1 & 2)

1 pF (Inputs 3 & 4)

4/26: 1 pF (Inputs 1 & 2)

1 pF (Inputs 3 & 4)

MΩ150

||

MΩ150

||

MΩ150

||

MΩ200

||

MΩ150

||

MΩ200

||

B Specifications

PowerLab Owner’s Guide

44

Input coupling: DC or 0.15 Hz (software selectable)

Maximum bandwidth: 25 kHz

DC drift: Software corrected

CMRR: > 105 dB at a gain of 100

Interchannel crosstalk: > 90 dB

Signal-noise ratio: > 100 dB (±10V range)

Accuracy error: Less than 0.2 %

Non-linearity (max): 0.1 %

Filters - Low pass: 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000,

2000 Hz and Anti-alias

- Notch: Mains

Pod Connectors (DIN)

General features: Combined power, I2C and single-ended or

differential analog input signals on one

connector, support SmartPod transducers,

etc.

Supply voltage: ±5 V regulated

Maximum current: 50 mA per pod connector

Communications: 2-wire I2C

Signal input: Positive and negative analog inputs and

analog return

Connector type: 8-pin DIN with metal surrounds

Sampling

ADC configuration Each channel has its own ADC

(2/26 and 15T have 2; 4/26 and 26T have 4)

ADC resolution: 24-bits

ADC linearity: ±0.0006 % FSR (INL)

Maximum sampling rates: 100 000 samples/s per channel (concurrent);

400 000 samples/s (aggregate)

Available sampling rates: 100 000 samples/s down to 10 min/sample

Appendix B Specifications 45

Bio Amp Input – Inputs 3 & 4 (PowerLab 15T & 26T)

Number of channels: 2

Input configuration: Differential with common isolated ground

Amplification ranges: Range Resolution

±20 mV 625 nV

±10 mV 313 nV

±5 mV 156 nV

±2 mV 62 nV

±1 mV 31 nV

±500 μV 15 nV

±200 μV 6 nV

±100 μV 3 nV

Gain accuracy: 1 %

Non-linearity: 1 %

Noise: < 1 μVrms (0.5 – 2 kHz)

Maximum input over-voltage: ±5 V

Input leakage current: < 4 μArms @ 120 V, 60 Hz

< 4 μArms @ 240 V, 50 Hz

DC blocking: ±0.3 V

Baseline restoration: Automatic or user-controlled

Input impedance: 100 MΩ to isolated ground (~500 pF per

lead) using supplied Bio Amp subject cable

and lead wires

Safety: IEC60601-1 and CSA approval

Isolation rating: 4000 V ACrms (1 minute)

IMRR: 130 dB

CMRR: 110 dB

Filters - High pass: Single pole 0.5 Hz and 10 Hz

- Low pass 10, 20, 50, 100, 200, 500, 1000, 2000 Hz

- Notch Mains

Audio output (26T only): Stereo output socket supplying an analog

audio signal from both bio amp channels.

Suitable for earphones, headphones and

PowerLab Owner’s Guide

46

most externally powered speakers.

Output is 300 mV at full scale.

Output Amplifier

Output configuration: 2 Outputs – Complementary

Output resolution: 16-bit

Maximum output current: 20 mA

Accuracy error: Less than 0.2 %

Linearity error: ±0.5 LSB (INL) (typical)

±0.5 LSB (DNL) (typical)

Output ranges: ±10 V

±5 V

±2 V

±1 V

±500 mV

±200 mV

Output slew rate: 2.3 V/μs

Settling time (G=1, 10 V step): 5 μs

Output impedance: 0.001 Ω

Isolated Stimulator Output (PowerLab 15T & 26T)

Output configuration: Constant-current stimulator with hardware

limited repetition rate

Isolation rating: 4000 Vrms to ground as per IEC60601-1

2000 Vrms to Bio Amp inputs

Pulse duration: 50 – 200 μs (software selectable)

Compliance voltage: 100–110 V typical

Output current: 0 – 20 mA in 0.1 mA steps (software

selectable)

Pulse rate: Software selectable, but hardware-limited to

a maximum of 1000 Hz and 200 μs for

safety.

Safety indicators: Green and yellow indicators. Green flash

indicates delivery of a valid stimulus.

Concurrent green and yellow flash indicates

an out-of-compliance condition.

Appendix B Specifications 47

Safety switch: Provides physical disconnection of the

stimulator from the subject.

External Trigger (not on PowerLab 15T)

Trigger mode: TTL level or contact closure, software

selectable

Trigger threshold: +1.3 V (rising edge), +1.1 V (falling edge)

Hysteresis: 0.3 V

Input load: HCMOS

Maximum input over-voltage: ±12 V

Minimum event time: 3 μs

Expansion Ports (not on PowerLab 15T)

I2C expansion port: Power and control bus for front-end units.

Supports a number of front-ends equal to

the number of PowerLab analog inputs.

Interface communications rate of up to

10 Kbits/s.

Digital ports (26T only)

- Output: 8 independent lines, TTL output level

(8 mA maximum load per line)

- Input: 8 independent lines, TTL input level,

threshold 1.2 V, 10 kΩ input impedance, 5V

maximum

Microprocessor and Data Communication

CPU: Digital Signal Processor – Freescale

DSP56858

RAM: 4 Mbit SRAM

ROM: 1 Mbit Flash ROM

Data communication: Hi-speed USB 2.0 (max of 480 Mb/s

transfer) compatible with USB 1.1 hosts.

Physical Configuration

Dimensions (h × w × d): 65 mm × 200 mm × 250 mm

(2.56" × 7.9" × 9.8")

Weight: 1.8 kg

PowerLab Owner’s Guide

48

Operating Requirements

Operating voltage range: 95–264 V AC, 47–63 Hz

Rated power: 25 VA

Operating conditions: 5–35 °C, 0–90 % humidity (non-

condensing)

ADInstruments reserves the right to alter these specifications at any time.

Electromagnetic Compatibility

The ML818 PowerLab 15T, ML826 PowerLab 2/26, ML846 PowerLab 4/26

and ML856 PowerLab 26T (the devices) have been tested to comply with IEC

60601-1-2:2004 (AS/NZS 3200.1.2) including IEC 61000-3-2, IEC 61000-3-3,

IEC 61000-4-2, IEC 61000-4-3, IEC 61000-4-4, IEC 61000-4-5, IEC 61000-4-

6, IEC 61000-4-8, IEC 61000-4-11 and CISPR 11 Group1 Class A.

Emissions

• The devices are suitable for use in all establishments other than domestic and

those directly connected to the public low-voltage power supply network that

supplies buildings used for domestic purposes. There may be potential difficulties

in ensuring electromagnetic compatibility in other environments, due to

conducted as well as radiated disturbances.

Immunity

See Table B–1 p. 49.

• Mains power quality should be that of a typical commercial or hospital

environment. If the user of the devices requires continued operation during power

mains interruptions, it is recommended that the devices be powered from an

uninterruptible power supply or a battery.

• Power frequency magnetic fields should be at levels characteristic of a typical

location in a typical commercial or hospital environment.

• Floors should be wood, concrete or ceramic tile. If floors are covered with

synthetic material, the relative humidity should be at least 30%.

Appendix B Specifications 49

Immunity test IEC 60601 test level Compliance level

Electromagnetic

environment

guidance

Conducted RF

IEC 61000-4-6

3 Vrms

150 kHz to 80 MHz

3 V Recommended separa-

tion distance

(see Table B–2 p. 50)

Radiated RF

IEC 61000-4-3

3 V/m

80 MHz to 2.5 GHz

3 V/m Recommended separa-

tion distance

(see Table B–2 p. 50)

Electrostatic dis-

charge

IEC61000-4-2

±6 kV contact

±8 kV air

±4 kV contact

±8 kV air

Floors should be wood,

concrete or ceramic tile.

If floors are covered with

synthetic material, the

relative humidity should

be at least 30%.

Electrical fast tran-

sient/burst

IEC61000-4-4

±2 kV for power supply

lines

±1 kV for input/output

lines

±2 kV for power supply

lines

±1 kV for input/output

lines

Mains power quality

should be that of a typi-

cal commercial or hospi-

tal environment.

Surge

IEC 61000-4-5

±1 kV differential mode

±2 kV common-mode

±1 kV differential mode

±2 kV common-mode

Mains power quality

should be that of a typi-

cal commercial or hospi-

tal environment.

Voltage dips, short

interruptions and

voltage variations

on power supply

input lines

IEC61000-4-11

<5% UT (>95 % dip in

UT) for 0.5 cycle

40% UT (60% dip in UT)

for 5 cycles

70% UT (30% dip in UT)

for 25 cycles

<5% UT (>95% dip in

UT) for 5 sec

<5% UT (>95% dip in

UT) for 0.5 cycle

40% UT (60% dip in UT)

for 5 cycles

70% UT (30% dip in UT)

for 25 cycles

Mains power quality

should be that of a typi-

cal commercial or hospi-

tal environment. If the

user of the devices

require continued opera-

tion during power mains

interruptions, it is recom-

mended that the devices

be powered from an

uninterruptible power

supply or a battery.

Power frequency

(50/60Hz) magnetic

field

IEC 61000-4-8

3 A/m 3 A/m Power frequency mag-

netic fields should be at

levels characteristic of a

typical location in a typi-

cal commercial or hospi-

tal environment.

Table B–1

Immunity test compliance

PowerLab Owner’s Guide

50

Separation Distances

• The devices are intended for use in an electromagnetic environment in which

radiated RF disturbances are controlled.

• Portable and mobile RF communications equipment should be used no closer to

any part of the devices, including cables, than the recommended separation

distance in the table below.

• Field strengths from fixed RF transmitters, as determined by an electromagnetic

site survey, should be less than the compliance level in each frequency range.

Separation distance

Rated maximum output

power of transmitter, P

150 kHz to 800 MHz 800 Mhz to 2.5 GHz

d = 1.17ÐP d = 2.33ÐP

0.01 W 0.1 m 0.2 m

0.1 W 0.4 m 0.7 m

1 W 1.2 m 2.3 m

10 W 3.7 m 7.4 m

100 W 11.7 m 23.4 m

Table B–2

Separation distances

Glossary 51

AC coupling. A filter option. When AC coupling is chosen, a 0.1 Hz high-

pass filter before the first amplification stage removes DC and frequency

components below 0.1 Hz. This removes slowly changing baselines.

ADC (analog-to-digital converter). A device that converts analog

information into some corresponding digital voltage or current.

amplitude. The maximum vertical distance of a periodic wave from the zero

or mean position about which the wave oscillates.

analog. Varying smoothly and continuously over a range. An analog signal

varies continuously over time, rather than changing in discrete steps.

analog input. This refers to the connectors on the front of the PowerLab

marked ‘Input’. These inputs are designed to accept up to ±10 volts. Inputs can

be either single-sided or differential (the latter only in the case of the pod

connectors).

analog output. This refers to the connectors on the front of the PowerLab

marked ‘Output’. The analog output provides a software-controlled variable

output (±10 V) that can be used with applications either directly as a

stimulator, or to control peripheral devices. Not for use with human subjects.

analysis. When the PowerLab is not physically connected to the computer,

then ADInstruments software can be used to analyze and manipulate existing

files if the analysis option is chosen.

BNC (bayonet nut connector). A type of cable or connector; a BNC-to-BNC

cable connects two BNC connectors.

bridge transducer. A type of transducer using a Wheatstone bridge circuit. In

its basic form, the bridge consists of four two-terminal elements (usually

strain gauges) connected to form a quadrilateral. An excitation source is

CGlossary

PowerLab Owner’s Guide

52

connected across one diagonal, and the transducer output is taken across the

other.

bus. A data-carrying electrical pathway (cables and connectors).

connector. A plug, socket, jack or port used to connect one electronic device

to another (via a cable): a PowerLab to a computer, say.

CPU (central processing unit). A hardware device that performs logical and

arithmetical operations on data as specified in the instructions: the heart of

most computers.

DAC (digital-to-analog converter). A device that converts digital

information into some corresponding analog voltage or current.

DC offset. The amount of DC (direct current) voltage present at the output of

an amplifier when zero voltage is applied to the input; or the amount of DC

voltage present in a transducer in its equilibrium state.

differential input. Input using both positive and negative inputs on a

PowerLab. The recorded signal is the difference between the positive and

negative input voltages: if both were fed exactly the same signal, zero would

result. Can reduce the noise from long leads.

DIN (Deutsche Industrie Norm). A type of cable or connector; there are

various sorts with different numbers of pins.

envelope form. The overall shape of a signal, outlined by the minimum and

maximum recorded values. Often used to display quickly changing signals.

excitation voltage. The voltage supplied to a bridge circuit from which the

transducer output signal is derived. Manipulating the transducer changes the

measurement elements of the bridge circuit, producing a change in its output

voltage.

external trigger. The input connector on the front of the PowerLab marked

‘Trigger’. This lets you start recording from an external source. The trigger

level (the voltage needed to have an effect) depends on the hardware and

cannot be changed. Recording can also be triggered by contact closure, if this

is set up in the software.

filter. An electronic device or a program that alters data in accordance with

specific criteria. Filters in hardware and software can be used to reduce or to

eliminate electronic noise or drift from data readings.

frequency. The number of complete cycles per second of a waveform.

Frequency is usually expressed in hertz: Hz (cycles per second), kilohertz:

Glossary 53

kHz (thousands of cycles per second), or megahertz: MHz (millions of cycles

per second).

frequency response. The bandwidth in which a circuit passes a signal without

too much attenuation. A low-pass filter’s frequency response is the frequency

where the output voltage becomes 0.707 (1/Ð2) of the input voltage or has

been attenuated by 3 decibels. If a low-pass filter has a frequency response of

200 Hz, say, then the signal is effectively unattenuated up to 150 Hz, and is

0.707 of the original value at 200 Hz.

front-end. An ancillary device that extends PowerLab capabilities, providing

additional signal conditioning and features for specialized work. Front-ends

are recognized automatically by the PowerLab system and seamlessly

integrated into its applications, operating under full software control.

gain. The amount of amplification of a signal.

half-bridge transducer. A bridge transducer only using half of the full-bridge

circuit. It consists of two elements of equal value with an excitation voltage

applied across them. The output of the transducer is taken at the junction of

the two elements.

hertz (Hz). The unit of frequency of vibration or oscillation, defined as the

number of cycles per second. For example, the minimum sampling rate for a

human ECG experiment should be 400 Hz (400 samples/s).

high-pass filter (HPF). A filter that passes high-frequency signals, but filters

low ones, by blocking DC voltages and attenuating frequencies below a certain

value (the cut-off, or –3 dB, frequency).

I2C (‘eye-squared-sea’). This connection is used by the PowerLab to control

front-ends. It provides power and communication using a

4-wire serial bus (two wires for standard I2C and two control lines).

IEC. International Electrotechnical Commission.

LabChart. An ADInstruments software application that emulates a multi-

channel chart recorder, with other powerful options. (Macintosh and

Windows versions differ slightly.)

LabTutor. An ADInstruments application for teaching physiology that

integrates the experiment protocol, real-time data acquisition, analysis and

reporting as interactive pages in the Internet Explorer browser.

low-pass filter (LPF). A filter that passes low-frequency signals and DC

voltages, but filters high ones, attenuating frequencies above a certain value

(the cut-off, or –3 dB, frequency).

PowerLab Owner’s Guide

54

MacLab. An earlier name for the PowerLab, before it became cross-platform.

PCI (peripheral component interconnect). A protocol for connecting

peripheral devices (such as USB cards) to computers and so on.

pod connector. A special 8-pin DIN connector on some PowerLabs giving

differential or single-sided connections for analog inputs. Pods can connect to

them, and they can also provide power and control for some types of

transducers.

pods. Small, low-cost units that connect to the PowerLab’s pod connectors.

They give alternatives to front-ends for specific tasks, for use with

precalibrated transducers and so on.

port. A socket where you plug in a cable for connection to a network or a

peripheral device. Also, any connection for transferring data, for instance

between the CPU and main memory.

PowerLab. The PowerLab hardware unit is a self-contained data acquisition

hardware unit that connects to a Windows or Macintosh computer. When

used in conjunction with programs such as LabTutor, LabChart and Scope, it

functions as a versatile laboratory instrument.

PowerLab system. The system consists of a hardware unit and applications

software (and possibly ancillary devices). It provides a multi-purpose data

recording, display, and analysis environment for experimental data.

range. In LabChart and Scope, the range is the greatest positive and negative

voltage that can be displayed, usually from ±5 mV to ±10 V, in 11 steps.

(Range is inversely proportional to gain, the extent of amplification.)

Scope. An ADInstruments software application that emulates a two-channel

storage oscilloscope, with added powerful options. (Macintosh and Windows

versions are very similar.)

serial. A connection protocol for sending information sequentially, one bit at

a time, over a single wire.

transducer. A physical device that converts a mechanical, thermal or

electrical stimulus into a proportional electrical output. For example, there are

common transducers to measure force, displacement, temperature, pressure,

and similar parameters.

trigger. A signal, such as a voltage pulse, used to determine when sampling

will begin. Sampling can be made to begin when the trigger level is reached,

after it, or even prior to it. See also external trigger.

Glossary 55

TTL (transistor-transistor logic). A family of integrated circuits (ICs) with

bipolar circuit logic, used in computers and related devices.

TTL is also a standard for interconnecting such ICs, defining the voltages

used to represent logical zeroes and ones (binary 0 and 1).

USB. Universal Serial Bus.

waveform. The shape of a wave; a graph of a wave’s amplitude over time.

PowerLab Owner’s Guide

56

Index 57

A

ADC (analog-to-digital converter) 34

ADInstruments contacts 12

analog input 15, 35

analog output 15, 34, 35

analog-to-digital converter 34

anti-aliasing 30

audio connector 18

B

back panel 17–19

Bio Amp

cable 19–20

inputs 16, 37

software 28–31

C

calibration 39

checking the PowerLab 12

compliance 16, 38

connections

audio 18

digital 18

front-ends 15, 41

ground 19

I2C 18, 40

pod 15, 41

power 19

PowerLab to computer 23, 41–42

safe, to humans 15

USB 18, 23, 41

contact addresses 12

D

DAC (digital-to-analog converter) 34

DC drift 35, 39

DC restore 30

digital input 18, 39

digital output 18, 39

digital-to-analog converter 34

E

earthing 42

electromagnetic compatibility 48–50

error patterns 22

external trigger 13, 36

F

filtering 29

front panel 13–16

front-ends 20

G

ground connection 19

ground loops 42

H

high-pass filter 30

I

Isolated Stimulator

output 16, 38

software 24–27

Isolated Stimulator panel 27

I2C connector 18, 40

L

LabChart 23

Index

PowerLab Owner’s Guide

58

low-pass filter 30

M

mains filter 30

marker 27

P

pod connection 15, 41

pods 20

Power indicator 13, 22

power switch 19

PowerLab

accuracy 39

back panel 17–19

calibration 39

connectors 39–42

front panel 13–16

input amplifiers 35

power supply 34

safety 15

self-test 22

S

safety 15

Safety Notes 5–10

safety switch 16

Scope 24

self-test 22

Status indicator 13, 22

stimulator controls 24–27

Stimulator Pulse indicator 16, 38

Stimulator software 24–27

storage 10

T

technical specifications 43–48

transducers 20

trigger 13

Trigger indicator 13

U

USB

connection 18, 23, 41

high-speed cables 41

port 42

user modification voids warranty 33