Bio Amp Owners Guide
Bio Amp Owner’s Guide
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, LabTutor and MacLab are registered trademarks of ADInstruments Pty Ltd. The names of speciﬁc recording units, such as PowerLab 8/30, are trademarks of ADInstruments Pty Ltd. Chart and Scope (application programs) are trademarks of ADInstruments Pty Ltd. Other Trademarks Apple, Mac and Macintosh are registered trademarks of Apple Computer, Inc. Windows, Windows 2000, Windows XP and Windows Vista are either registered trademarks or trademarks of Microsoft Corporation. All other trademarks are the property of their respective owners.
Product: ML132 Bio Amp; ML135 Dual Bio Amp; ML138 Octal Bio Amp Document Number: U-ML132-OG-004A Part Number: 4377 Copyright © August 2007 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: Technical Support: Documentation:
ADInstruments Pty Ltd. ISO 9001:2000 Certiﬁed Quality Management System Reg. No. 1053
Bio Amp Owner’s Guide
How to Use This Guide... 14 Checking the Front-end... 14 Front-end Fundamentals... 14 The Front-end... 15 The Front Panel... 15 The Input Socket... 16 The Status Indicator... 17 Audio Out Socket... 17 The Back Panel... 17 I2C Input and Output Sockets... 17 Analog Output Sockets... 17 Audio Out Socket... 18 The Bio Amp Cable... 19 Types of Measurement... 20 Recording Technique... 21
2 Setting Up
Connecting to the PowerLab... 24 Using More Than One Bio Amp... 25 Using ADInstruments Programs... 26 The Front-end Driver... 26 The Bio Amp Self-test... 26 Software Behavior... 27 The Bio Amp... 27 Signal Display... 27 Setting the Range... 29 Filtering... 29 EEG Mode... 30 Inverting the Signal... 30 Units... 31 DC Restore... 31
A Technical Aspects
Bio Amp Operation... 36 Technical Description... 36 The Bio Amp Cable Input... 37
Single Bio Amp... 43 Input... 43 Filtering... 44 Output... 44 Control Port... 44 Physical Configuration... 45 Safety... 45 Dual Bio Amp... 45 Input... 45 Filtering... 46 Output... 47 Control Port... 47 Physical Configuration... 47 Safety... 47 Octal Bio Amp... 48 Input... 48 Filtering... 49 Output... 49 Control Port... 49 Physical Configuration... 49 Safety... 49
Bio Amp Owner’s Guide
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 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.
! BF symbol: Bodyprotected equipment
CF symbol: Cardiacprotected equipment
Warning symbol: ‘see documentation’
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:
Bio Amp Owner’s Guide
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-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).
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.
Bio Amp Owner’s Guide
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: • •
• • •
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) 9
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 socketoutlets 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.
Cleaning and Sterilization ADInstruments products may be wiped down with a lint free cloth moistened with industrial methylated spirit. Refer to 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.
Bio Amp Owner’s Guide
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%.
Temperature in the range 0–35 °C Non-condensing humidity in the range 0–90%.
Forward to recycling center or return to manufacturer.
Bio Amp Owner’s Guide
The Bio Amp is a modular device, in a family called front-ends, designed to extend the capabilities of the PowerLab system. The Bio Amp allows the PowerLab system to record biological signals, such as ECGs (EKGs), EMGs, and EEGs, from humans or animals, with full electrical isolation. This chapter provides an overview of the Bio Amp, Dual Bio Amp and Octal Bio Amp, describing their basic features and the measurement of signals.
Chapter 1 Overview
How to Use This Guide This owner’s guide describes how to set up and begin using your Bio Amp. The chapters give an overview of front-ends in general and the Bio Amp in particular, and discuss how to connect the hardware, perform a simple power-up test, and use the Bio Amp with some ADInstruments programs. The appendices provide technical information about the Bio Amp, and take a look at some potential problems and their solutions. There is an index at the end of this guide. Technical terms that are not deﬁned in the glossary of terms included with the owner’s guide for your PowerLab, or in the guide that came with your computer, are deﬁned as they appear.
Checking the Front-end Before connecting the Bio Amp to anything, check it carefully for signs of physical damage. 1. Check that there are no obvious signs of damage to the outside of the front-end casing. 2. Check that there is no obvious sign of internal damage, such as rattling. Pick up the front-end, tilt it gently from side to side, and listen for anything that appears to be loose. If you have found a problem, contact your authorized ADInstruments representative immediately, and describe the problem.
Front-end Fundamentals The PowerLab system consists of a recording unit and application programs that run on the computer to which the unit is connected. It is an integrated system of hardware and software designed to record, display, and analyze experimental data. The Bio Amp is one of a family of front-ends meant for use with your PowerLab system. Front-ends are ancillary devices connected to the PowerLab recording unit to extend the system’s capabilities. They provide additional signal conditioning and other features, and extend the types of experiments that you can conduct and the data you can record.
Bio Amp Owner’s Guide
All ADInstruments front-ends are designed to be operated under full software control. No knobs, dials, or switches are needed, although some may be provided for reasons of convenience or safety. The PowerLab controls front-ends through an expansion connector called the I2C (pronounced ‘eye-squared-sea’) bus. Each front-end added to the system connects to the back of the previous front-end, in a simple daisy-chain structure. This makes it easy to add front-ends to the system or to transfer them between PowerLabs. In general, each front-end requires at least one analog input channel of the PowerLab. Front-ends are automatically recognized by the PowerLab system. Any front-end feature such as gain or ﬁltering is combined with the appropriate features of the program and presented as a single set of software controls.
The Front-end The Bio Amp is designed to allow the PowerLab system to perform isolated measurements of biological signals - such as ECGs (EKGs), EMGs, and EEGs - from humans or animals. All Bio Amps consist of electrically isolated differential input AC ampliﬁers with common isolated ground connections. The number of ampliﬁers corresponds to the number of Bio Amp channels. For example, the Dual Bio Amp has two ampliﬁers with a shared ground connector and input socket, and the Octal Bio Amp has eight differential ampliﬁers with a shared ground connector and separate inputs. The Bio Amp is not isolated by itself. For multiple biological recordings (more than two) from a single subject it is recommended that you use a multi-channel Bio Amp rather than “daisy-chaining” multiple Bio Amps.
The Front Panel The front panel of a Bio Amp has a single input and an indicator light. The front panel of a Dual Bio Amp has a single input, two indicator lights and an audio output connector. The front panel of the Octal Bio Amp has seventeen single-ended 1.5 mm sockets consisting of eight red connectors, eight black connectors and a single green connector. A stereo audio connector is shared between adjacent Bio Amp inputs. Chapter 1 Overview
Figure 1–1 The front panels of the Bio Amp, Dual Bio Amp and Octal Bio Amp
Input socket Status indicator
The Input Socket
Connections are made to the Bio Amp and Dual Bio Amp using the six-pin socket on the front panel. The socket is physically and electrically isolated from the low-voltage mains-supply circuitry of the PowerLab, and the input connections are isolated internally, by isolation circuitry. The socket is of a sort commonly used with ECGtype cables and leads, such as the Bio Amp cable and leads with which your Bio Amp is supplied (Tronomed D-1340 or Tronomed D1540). The single Bio Amp and Dual Bio Amp have different pin arrangements, so their Bio Amp cables are not interchangeable. The socket and connections to it are discussed in more detail later on. Connections are made to the Octal Bio Amp using individual lead wires (supplied with every unit) and a common ground, rather than using a single multi-pin socket. Each of the eight Bio Amp inputs has one red and one black connector and an indicator light. The green connector is a shared ground connection across all eight inputs.
Bio Amp Owner’s Guide
The Status Indicator
The status indicator light of a single Bio Amp is located at the bottom right of the front panel. The status indicator lights of a Dual Bio Amp are located beneath the input connector on the front panel. The status indicator lights of an Octal Bio Amp are located beneath the pair of red and black connectors of each input on the front panel. When an ADInstruments application such as Chart starts, the status indicators should ﬂash brieﬂy and then remain green, indicating that the program has found the front-end, checked and selected it, and is ready to use it. If a status indicator does not turn on and stay on when the application starts, it is most likely that the front-end is not connected properly. Audio Out Socket
The Dual Bio Amp and Octal Bio Amp have audio monitor outputs on the front panel that can be used with a wide range of headphones or externally powered speakers. The 3.5 mm stereo socket provides two channels of sound, one for each data channel. The audio output may be of use when monitoring nerve ﬁrings to control the placement of electrodes, for instance.
The Back Panel The back panel of the Bio Amp provides all the sockets required to connect the front-end to the PowerLab and to other front-ends. I2C Input and Output Sockets
Two nine-pin sockets are used to communicate with the PowerLab (they are marked ‘I2C’ or ‘I2C Bus’: a ‘bus’ is simply informationtransmission circuitry such as cables and connectors). These sockets, in conjunction with the proper cables, allow multiple front-ends to be used independently with one PowerLab. Power and control signals to connected front-ends come from the PowerLab. ADInstruments frontends are connected to each other in series, output to input (this is discussed in more detail in the next chapter). Analog Output Sockets
BNC sockets on the back panels of the Bio Amps provide the signal outputs to connect to the analog input sockets on the front of the PowerLab. Chapter 1 Overview
Figure 1–2 The back panels of the Bio Amp, Dual Bio Amp and Octal Bio Amp
Signal Output to the PowerLab I2C connection to other front-ends
I2C connection to the PowerLab
The sockets are labeled Signal Output on a single Bio Amp and Output 1 to Output n on a multi-channel Bio Amp. A BNC-to-BNC cable is supplied for each connection. It is recommended that, to avoid confusion, you match the Bio Amp output number with the corresponding PowerLab input connector. If you are connecting to an earlier model PowerLab with differential inputs, only connect the Bio Amp output to the positive analog input of the PowerLab. ADInstruments applications do not ﬁnd a front-end on start-up if the negative input is used. Audio Out Socket
The single Bio Amp has an audio monitor output on the back panel that can be used with a wide range of headphones or externally powered speakers. The 3.5 mm stereo socket provides mono sound. The audio output may be of use when monitoring nerve ﬁrings to control the placement of electrodes, for instance. 18
Bio Amp Owner’s Guide
The Bio Amp Cable Connections are made to the Bio Amp and Dual 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. Note that the single Bio Amp and Dual Bio Amp have different pin arrangements, so their Bio Amp cables are not interchangeable. The single Bio Amp is supplied with a 3-lead Bio Amp cable and lead wires. The Dual Bio Amp is supplied with a 5-lead Bio Amp cable and lead wires; it uses a shared ground signal for its Bio Amp inputs. The supplied cables are of the type used for ECG or EMG studies: Tronomed D-1340 or Tronomed D-1540 cables respectively. The cable has a yoke with three or ﬁve sockets for the lead wires. Note that the active pins of a shielded cable are those closest to the label. Figure 1–3 Bio Amp cable yokes, with leads attached: 3 leads for the Bio Amp, and 5 leads for the Dual Bio Amp
To Bio Amp
To Dual Bio Amp
The lead wires supplied are of the type used for ECG studies. They click into place in the cable yoke, and have snap connectors at the other end to connect to typical ECG electrodes. The leads are colorcoded for identiﬁcation. The labels on the Bio Amp cable also have color spots to help sort out which cables connect where and what they are measuring. (The colors are arbitrary, since the PowerLab system is for general-purpose recording.) Connections to the Octal Bio Amp inputs can be made with the supplied lead wires. The input sockets are for unshielded, singleended lead wires with a 2 mm inside diameter with 1.5 mm pins. 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 electrodes), and abrasive gel, for lightly abrading the skin before the electrodes are attached. Chapter 1 Overview
Types of Measurement Standard electrophysiology texts describe various standard signals and how to measure them. ADInstruments also produces materials describing speciﬁc uses of Bio Amps, such as Application Notes, that can be downloaded from the ADInstruments website or obtained from your ADInstruments representative. The Bio Amp can measure a wide variety of biological signal sources. Some of these measurements include: ECG. Electrocardiogram (also referred to as EKG); a recording of surface potentials due to electrical currents associated with the heartbeat. EEG. Electroencephalogram; a recording of the electrical activity of the brain. Scalp electrodes record potential waves (10–100 μV) representing the summed activity of cortical neurons. EMG. Electromyography; a recording of the electrical activity of a muscle, using surface electrodes. The recorded activity may be a voluntary contraction, or evoked by motor nerve stimulation. EOG. Electro-oculogram; a recording of the potential difference between the front and back of the eyeball, as projected on to the face. Bilateral measurements require a Dual Bio Amp, or two Bio Amps. ERG. Electroretinogram; a recording of the electrical signals produced in the retina by a light stimulus. Bilateral measurements require a Dual Bio Amp, or two Bio Amps. Cortical Evoked Potentials. Averaged recordings of the electrical activity of the brain when subject to stimulation: visual evoked response, auditory evoked response, and somatosensory response. These should be done with signal averaging, using Scope. SNAP. Sensory nerve action potential; a recording of evoked responses in stimulated nerves. This is usually done with signal averaging, using Scope. Bio Amps are unsuitable for: •
work requiring high-impedance electrodes or a high bandwidth. Such tasks include intracellular micropipette recordings, which are made from a very ﬁne, electrolyte-ﬁlled tube inserted into a nerve or muscle cell, and require an electrometer ampliﬁer, and Bio Amp Owner’s Guide