Aspect Medical Systems A-2000 Service Manual
Aspect Medical Systems
TM
A-2000
BISPECTRAL INDEX
(BIS
) MONITORING SYSTEM
S E R V I C E M A N U A L
Caution:
U.S. Federal law restricts this device
to sale by or on the order of a physician.
© Copyright, 1999, Aspect Medical Systems. All rights reserved. Copying or other reproduction of
this document is prohibited without prior written consent of Aspect Medical Systems.
2 Vision Drive
Natick, MA 01760-2059
U.S.A.
508-653-0603
800-442-7688
bis_info@aspectms.com
www.aspectms.com 075-0002 1.00
Aspect Medical Systems, Inc.
TABLE OF CONTENTS
1. INTRODUCTION .............................................................................. 1-1
1.1 ABOUT THIS MANUAL ....................................................................................1-1
1.2 INTRODUCING THE A-2000 BIS MONITORING SYSTEM ............................. 1-2
1.2.1 Principal Components ................................................................................1-2
1.2.2 How The A-2000 Works .............................................................................1-3
1.3 INSTRUMENT IDENTIFICATION .....................................................................1-3
1.3.1 A-2000 Monitor ...........................................................................................1-3
1.3.2 A-2000 Digital Signal Converter .................................................................1-3
1.3.3 Software Revision Numbers .......................................................................1-3
1.4 PROPRIETARY INFORMATION AND DEVICES.............................................1-3
2. SAFETY PRECAUTIONS................................................................. 2-1
2.1.1 WARNINGS, CAUTIONS, AND NOTES .................................................... 2-1
2.1.2 Warnings: ...................................................................................................2-1
2.1.3 Cautions: ....................................................................................................2-3
2.2 KEY TO SYMBOLS ..........................................................................................2-5
3. PRINCIPLES OF OPERATION........................................................ 3-1
3.1 SYSTEM ARCHITECTURE............................................................................... 3-1
3.1.1 The Digital Signal Converter (DSC)............................................................3-1
3.1.2 The A-2000 Monitor....................................................................................3-7
3.1.3 A-2000 Printer ............................................................................................3-8
4. PREPARATION FOR USE AND INSTALLATION ........................... 4-1
4.1 ENVIRONMENT ................................................................................................4-1
4.1.1 Shipping and Storage Environment............................................................4-1
4.1.2 Operating Environment...............................................................................4-1
4.1.3 Power Requirements and System Grounding ............................................4-2
4.1.4 Site Preparation..........................................................................................4-2
4.2 INSTRUMENT CONNECTIONS .......................................................................4-3
4.2.1 Digital Signal Converter Connections.........................................................4-3
4.2.2 Power Cord Connections............................................................................4-3
4.2.3 Printer Connector .......................................................................................4-3
4.3 INSTALLATION AND VERIFICATION PROCEDURE .....................................4-4
4.4 REPACKAGING FOR SHIPPING AND STORAGE.......................................... 4-4
5. PREVENTIVE MAINTENANCE, CARE AND CLEANING ............... 5-1
5.1 CARE AND CLEANING ....................................................................................5-1
5.1.1 Cleaning the Monitor and Digital Signal Converter.....................................5-1
5.1.2 Disinfecting the Monitor and Digital Signal Converter ................................5-1
5.1.3 Cleaning the Monitor Display......................................................................5-1
5.2 ROUTINE MAINTENANCE ...............................................................................5-2
5.2.1 Checking the Battery ..................................................................................5-2
5.2.2 Checking Leakage Current.........................................................................5-2
5.2.3 Monitor System Checkout Procedure.........................................................5-4
5.2.4 DSC Checkout Procedure ..........................................................................5-5
5.2.5 Patient Interface Cable (PIC) Checkout Procedure....................................5-5
6. DIAGNOSTICS AND TROUBLESHOOTING................................... 6-1
6.1 GENERAL TROUBLESHOOTING.................................................................... 6-1
6.2 THE A-2000 DIAGNOSTIC PROCEDURES.....................................................6-4
6.2.1 Power-Up Diagnostics ................................................................................6-4
6.2.2 Automatic Diagnostics ................................................................................6-8
6.2.3 Manual Diagnostics ..................................................................................6-13
7. DISASSEMBLING AND REASSEMBLING THE A-2000................. 7-1
7.1 REQUIRED TOOLS AND SUPPLIES...............................................................7-2
7.2 THE MONITOR CASE.......................................................................................7-3
7.2.1 Opening the Monitor Case..........................................................................7-3
7.2.2 Closing the Monitor Case ...........................................................................7-3
7.3 THE ELECTRO/LUMINESCENT DISPLAY......................................................7-7
7.3.1 Removing the E/L Display Board................................................................7-7
7.3.2 Reattaching the E/L Display Board.............................................................7-7
7.4 THE FRONT PANEL SWITCH SET..................................................................7-9
7.4.1 Removing the Switch Set ...........................................................................7-9
7.4.2 Installing the New Switch Set .....................................................................7-9
7.5 THE PRINTED CIRCUIT BOARD ASSEMBLY ..............................................7-11
7.5.1 Removing the Printed Circuit Board assembly ......................................... 7-11
7.5.2 Installing the Printed Circuit Board Assembly...........................................7-11
7.6 THE MAIN PCB...............................................................................................7-14
7.6.1 Removing the Main PCB ..........................................................................7-14
7.6.2 Installing the Main PCB ............................................................................7-14
7.7 THE POWER SUPPLY PCB ...........................................................................7-19
7.7.1 Removing the Power Supply PCB............................................................7-19
7.7.2 Installing the Power Supply PCB..............................................................7-19
7.8 THE BATTERY................................................................................................ 7-22
7.8.1 Removing the Battery ...............................................................................7-22
7.8.2 Installing the Battery .................................................................................7-22
7.9 THE FAN .........................................................................................................7-24
7.9.1 Removing the Fan ....................................................................................7-24
7.9.2 Installing the Fan ......................................................................................7-24
7.10 THE CLAMP SHOE ASSEMBLY.................................................................... 7-26
7.10.1 Removing the Clamp Shoe Assembly ...................................................... 7-26
7.10.2 Installing the Clamp Shoe Assembly ........................................................ 7-26
7.11 FUSE REPLACEMENT...................................................................................7-27
8. A-2000 SPECIFICATIONS.............................................................. 8-1
8.1 GENERAL SPECIFICATIONS:.........................................................................8-1
8.1.1 Type of Protection against Electric Shock of the System: .......................... 8-3
8.1.2 Degree of Protection against Electric Shock of the System: ......................8-3
8.1.3 Degree of Protection against the Ingress of Water: ...................................8-3
8.1.4 Mode of Operation of the System:..............................................................8-3
8.1.5 Classification: .............................................................................................8-3
8.2 OPTIONS AND ACCESSORIES:......................................................................8-3
8.3 Digital Signal Converter (DSC) Connector....................................................8-4
8.4 WARRANTY......................................................................................................8-5
9. APPENDICES .................................................................................. 9-1
9.1 APPENDIX I - A-2000 PARTS LIST................................................................ 9-1
9.2 APPENDIX II - SENSOR SIMULATOR - INSTRUCTIONS FOR USE ...........9-2
TABLE OF FIGURES
Figure 1-1 The A-2000 BIS Monitoring System................................................................1-4
Figure 1-2 Rear View of Monitor .....................................................................................1-5
Figure 3-1 The A-2000 System Block Diagram................................................................3-2
Figure 3-2 The A-2000 Signal Flow Diagram...................................................................3-3
Figure 3-3 The Digital Signal Converter (DSC)................................................................3-6
Figure 7-1 Opening the Monitor Case............................................................................7-5
Figure 7-2 The E/L Display Cable ...................................................................................7-5
Figure 7-3 The Keypad Cable Tension Flange ...............................................................7-6
Figure 7-4 The Four Mounting Screws............................................................................7-8
Figure 7-5 The Cable Access Port ................................................................................7-10
Figure 7-6 Remove the covering on the back of the new switch set.............................7-10
Figure 7-7 Place rear case assembly face down on a scratch free work surface.........7-13
Figure 7-8 Fan Cable ....................................................................................................7-13
Figure 7-9 Release standoff tab by squeezing with needle-nose pliers........................7-15
Figure 7-10 The L bracket.............................................................................................7-15
Figure 7-11 Gently pull and flex to separate PCBs .......................................................7-16
Figure 7-12 Line up Interconnect PCB pins to Main PCB socket..................................7-16
Figure 7-13 Align standoffs and push in until standoff tabs snap into place .................7-17
Figure 7-14 Install L bracket by holding long side; short side connects to Main PCB...7-17
Figure 7-15 The L Bracket Installed ..............................................................................7-18
Figure 7-16 Gently flex and pull Power Supply PCB free of pins ..................................7-20
Figure 7-17 Remove four screws on rear of Power Supply PCB..................................7-20
Figure 7-18 Remove shield from rear of Power Supply PCB........................................7-21
Figure 7-19 Battery and cable.......................................................................................7-23
Figure 7-20 Fan wiring orientation and Clamp Shoe screws ........................................7-25
Figure 7-21 Updated System with 2 Fan Mounting screws and Copper Tape..............7-25
Figure 7-22 Releasing the plastic locking tabs of the fuse holder.................................7-28
Figure 7-23 Re-installing the fuse holder ......................................................................7-28
SECTION I INTRODUCTION
SECTION I
1.
INTRODUCTION
1.1
This Service Manual contains information necessary to diagnose, troubleshoot and repair
the Aspect Medical Systems A-2000™ BIS Monitoring System. Also included are
instructions for the unit’s installation, maintenance, care and cleaning. A parts list is
provided in the appendices at the back of the manual.
This manual is intended for Aspect Medical Systems service technicians and/or
authorized Aspect distributors who have been trained by Aspect to perform the service
procedures described within this manual. It assumes prior knowledge and experience
with the internal workings of medical devices and electronics.
Section I provides a functional overview of the A-2000, its principal components, and
instrument identification.
Section II discusses important safety precautions. Before attempting to set up or service
the A-2000, please familiarize yourself with the safety information provided in this section.
Section III describes the A-2000 monitor hardware and how it operates. Included are the
assemblies and parts that make up the monitor and the Digital Signal Converter (DSC).
Section IV provides preparation for use and installation instructions, including
environmental considerations, instrument connections and system setup and check out.
Section V describes normal maintenance, care and cleaning procedures.
Section VI describes the A-2000 diagnostic tools and provides tables to aid in
troubleshooting the system.
Section VII describes the removal and replacement procedure for each subassembly.
Section VIII contains the A-2000 specifications.
Appendix I contains a list of replaceable parts and subassemblies.
Appendix II contains the Sensor Simulator instructions for use.
ABOUT THIS MANUAL
Caution:
Refer to the section on disassembling and reassembling before
attempting to service the inside of the A-2000.
Note:
This manual was not designed for repairing the unit to the level of its
individual components (e.g. the chips on the main board). The manual is
intended solely for the troubleshooting and replacement of its
subassembly modules (e.g. the electro-luminescent display and power
supply).
- 1-1 -
SECTION I INTRODUCTION
1.2
Aspect Medical Systems A-2000 BIS Monitoring System is a user-configurable patient
monitoring system designed to monitor the hypnotic state of the brain based on
acquisition and processing of EEG signals. The A-2000 processes raw EEG signals to
produce a single number, called the Bispectral Index, or BIS, which correlates to the
patient’s level of hypnosis. It operates from an AC power source of 100V to 240V,
47/63Hz, and provides a minimum 20 minutes of automatic back-up battery power.
The monitor is menu-driven with fixed keys for choosing the options available.
1.2.1
The system is composed of a monitor and a digital signal converter, with a patient
interface cable (PIC), and BIS Sensor.
1.2.1.1 Monitor
The monitor contains the operator control panel, an electro-luminescent display screen,
and connectors for the digital signal converter and printer.
Front Panel Controls:
INTRODUCING THE A-2000 BIS MONITORING SYSTEM
Principal Components
The [SILENCE] key toggles audible alarms on and off.
The left [←] and right [→] arrow keys are used to enter Review
mode and to scroll data back and forth while in Review mode.
The [MENU/EXIT] key is used to enter and exit the Setup Menu.
In Review mode it will return the user to the main screen. It is
also used to halt certain procedures, such as the sensor check,
and to answer "no" to a question.
The up [↑] and down [↓] arrows are used to move from one
menu selection to another.
The [SELECT] key is used to move between menu selections, to
confirm an entry, and to answer "yes" to a question.
- 1-2 -
SECTION I INTRODUCTION
1.2.1.2 Digital Signal Converter (DSC)
The Digital Signal Converter is about the size of a computer mouse. It contains the EEG
amplifiers and analog filters. The DSC digitizes EEG waveforms for transmission to, and
processing by, the monitor. The DSC’s long flexible Monitor Interface Cable connects to
the front of the monitor, and the shorter “DSC pigtail” cable connects to the Patient
Interface Cable (PIC).
The attachment clip on the DSC is used to secure it in a convenient location near the
patient’s head. The patient connection is accomplished by attaching the Aspect BIS
Sensor to the PIC.
1.2.2
A detailed description of how the A-2000 works is contained within Section V of the A2000 Operating Manual and will not be discussed in this Service Manual. Please refer to
the A-2000 Operating Manual (070-0015) for additional information.
1.3
1.3.1
Monitor identification information is permanently marked on the rear panel. This
information includes instrument model and serial numbers, power ratings, cautions, and
the Aspect Medical Systems shipping address.
1.3.2
The A-2000 Digital Signal Converter identification information is permanently marked on
the rear panel of the Digital Signal Converter. This information includes instrument model
and serial numbers and cautions.
1.3.3
Software revision numbers are displayed in the Diagnostic Menu.
1.4
Information and descriptions contained in this guide are the property of Aspect Medical
Systems and may not be copied, reproduced or distributed without prior written
permission. Portions of the A-2000 design are proprietary and are the subject of patents
and patents pending.
How The A-2000 Works
INSTRUMENT IDENTIFICATION
A-2000 Monitor
A-2000 Digital Signal Converter
Software Revision Numbers
PROPRIETARY INFORMATION AND DEVICES
- 1-3 -
SECTION I INTRODUCTION
Figure 1-1 The A-2000 BIS Monitoring System
- 1-4 -
SECTION I INTRODUCTION
Potential
Equalization
Terminal
Clamp
Shoe
Fuse
Holder
Serial
Port
Figure 1-2 Rear View of Monitor
- 1-5 -
SECTION I INTRODUCTION
- 1-6 -
SECTION II SAFETY PRECAUTIONS
SECTION II
2.
SAFETY PRECAUTIONS
INTRODUCTION
Caution:
Carefully read the entire A-2000 Operating Manual before using the monitor in a
clinical setting.
2.1.1
The terms warning, caution, and note have specific meanings in this manual.
• A WARNING advises against certain actions or situations that could result in personal
• A CAUTION advises against actions or situations that could damage equipment,
• A NOTE provides useful information regarding a function or procedure.
KEY TO SYMBOLS
A key to the symbols used on the A-2000 appears at the end of this section.
2.1.2
EXPLOSION HAZARD: DO NOT USE THE A-2000 IN A FLAMMABLE ATMOSPHERE
OR WHERE CONCENTRATIONS OF FLAMMABLE ANESTHETICS MAY OCCUR.
FOR PROPER GROUNDING, THE POWER RECEPTACLE MUST BE A THREE-WIRE
GROUNDED OUTLET. A HOSPITAL GRADE OUTLET IS REQUIRED. NEVER
ADAPT THE THREE-PRONG PLUG FROM THE MONITOR TO FIT A TWO-SLOT
OUTLET. IF THE OUTLET HAS ONLY TWO SLOTS, MAKE SURE THAT IT IS
REPLACED WITH A THREE-SLOT GROUNDED OUTLET BEFORE ATTEMPTING TO
OPERATE THE MONITOR.
IF THE INTEGRITY OF THE EXTERNAL PROTECTIVE EARTH GROUND IS IN
DOUBT, THE A-2000 SHALL BE OPERATED FROM ITS INTERNAL BATTERY
POWER SOURCE ONLY.
GROUND WIRE LEAKAGE CURRENT MUST BE CHECKED WHENEVER
INSTRUMENT CASE IS OPENED BY A QUALIFIED BIOMEDICAL ENGINEERING
TECHNICIAN.
ELECTRICAL SHOCK HAZARD: THE MANUFACTURER’S INSPECTION OF THIS
APPARATUS VERIFIED THAT THE GROUND LEAKAGE CURRENT AND THE
PATIENT SAFETY CURRENT WERE LESS THAN THE SPECIFIED LIMITS
ESTABLISHED BY THE APPLICABLE SAFETY STANDARDS. AS A MATTER OF
SAFE PRACTICE, THE INSTITUTION SHOULD CONDUCT PERIODIC TESTS TO
VERIFY THESE CURRENTS. WHENEVER AN EVENT SUCH AS SPILLAGE OF
BLOOD OR SOLUTIONS OCCURS, RE-TEST BEFORE FURTHER USE.
WARNINGS, CAUTIONS, AND NOTES
injury or death.
produce inaccurate data, or invalidate a procedure, although personal injury is
unlikely.
Warnings:
- 2-1 -
SECTION II SAFETY PRECAUTIONS
UNIVERSAL PRECAUTIONS SHALL BE OBSERVED TO PREVENT CONTACT WITH
BLOOD OR OTHER POTENTIALLY INFECTIOUS MATERIALS. PLACE
CONTAMINATED MATERIALS IN REGULATED WASTE CONTAINER.
DO NOT MIX DISINFECTING SOLUTIONS (e.g. BLEACH AND AMMONIA) AS
HAZARDOUS GASES MAY RESULT.
ELECTRICAL SHOCK HAZARD: DO NOT REMOVE MONITOR COVERS DURING
OPERATION OR WHILE POWER IS CONNECTED TO MONITOR.
FOR CONTINUED PROTECTION AGAINST FIRE OR DAMAGE, ALWAYS REPLACE
OLD FUSE WITH THE SAME FUSE TYPE AND RATING.
ANY PROCEDURES THAT REQUIRE THE REMOVAL OF THE MONITOR’S COVER
AND INTERNAL PARTS SHOULD BE PERFORMED BY A QUALIFIED BIOMEDICAL
ENGINEERING TECHNICIAN. POWER OFF THE UNIT USING THE POWER SWITCH.
UNPLUG THE MONITOR BEFORE DISASSEMBLING/ REASSEMBLING THE
A-2000.
IF METAL COMES IN CONTACT WITH THE TERMINALS ON THE BATTERY, IT
COULD RESULT IN PERMANENT DAMAGE TO THE BATTERY AND IS AN
ELECTRICAL SHOCK HAZARD.
DUE TO THE BATTERY OPERATION POSSIBLE WITH NO AC CONNECTED,
EXTREME CARE MUST BE USED WHEN DISASSEMBLING AND ASSEMBLING THE
A-2000 MONITOR. WITH AC DISCONNECTED AND BATTERY POWER ON, HIGH
VOLTAGE IS PRESENT ON THE E/L DISPLAY AND POWER SUPPLY PCB. DO NOT
ACTIVATE POWER ON SWITCH WITH CASE OPEN!
SHOCK HAZARD: DO NOT ATTEMPT TO DISCONNECT THE POWER CORD WITH
WET HANDS. MAKE CERTAIN THAT YOUR HANDS ARE CLEAN AND DRY BEFORE
TOUCHING THE POWER CORD.
FOR A-2000s USED OUTSIDE OF NORTH AMERICA: A HARMONIZED LINE CORD
WITH CONDUCTORS HAVING A CROSS SECTIONAL AREA GREATER THAN 0.75
MM2 MUST BE USED.
THE CONDUCTIVE PARTS OF ELECTRODES OR SENSOR AND CONNECTORS,
INCLUDING THE NEUTRAL ELECTRODE, SHOULD NOT CONTACT OTHER
CONDUCTIVE PARTS INCLUDING EARTH.
TO REDUCE THE HAZARD OF BURNS IN THE HIGH FREQUENCY SURGICAL
NEUTRAL ELECTRODE CONNECTION, THE SENSOR OR ELECTRODES SHOULD
NOT BE LOCATED BETWEEN THE SURGICAL SITE AND THE ELECTRO-SURGICAL
UNIT RETURN ELECTRODE.
TO MINIMIZE THE RISK OF PATIENT STRANGULATION, THE PATIENT INTERFACE
CABLE (PIC) MUST BE CAREFULLY PLACED AND SECURED.
BE SURE MONITOR IS MOUNTED SECURELY IN PLACE TO AVOID PERSONAL
INJURY.
- 2-2 -
SECTION II SAFETY PRECAUTIONS
WHEN CONNECTING EXTERNAL EQUIPMENT (e.g. DATA CAPTURE COMPUTER),
THE SYSTEM LEAKAGE CURRENT MUST BE CHECKED AND MUST BE LESS
THAN THE IEC601-1-1 LIMIT.
THE USE OF ACCESSORY EQUIPMENT NOT COMPLYING WITH THE EQUIVALENT
SAFETY REQUIREMENTS OF THIS EQUIPMENT MAY LEAD TO A REDUCED LEVEL
OF SAFETY OF THE RESULTING SYSTEM. CONSIDERATION RELATING TO THE
CHOICE SHALL INCLUDE:
• USE OF THE ACCESSORY IN THE PATIENT VICINITY;
• EVIDENCE THAT THE SAFETY CERTIFICATION OF THE ACCESSORY HAS
BEEN PERFORMED IN ACCORDANCE TO THE APPROPRIATE IEC 601-1
AND/OR IEC 601-1-1 HARMONIZED NATIONAL STANDARD.
FAN WIRE MUST BE POSITIONED AS SHOWN IN FIG. 7-21. INCORRECT ROUTING
OF FAN WIRE MAY RESULT IN A HAZAROUS CONDITION.
2.1.3
Cautions:
U.S. Federal law restricts this device to sale by or on the order of a physician.
Refer to the section on disassembling and reassembling before attempting to
service the inside of the A-2000.
Carefully read the entire A-2000 Operating Manual before using the monitor in a
clinical setting.
Periodically check the battery by operating an A-2000 that has been disconnected
from the wall socket and which has been charging the battery for at least four
hours. After long periods of storage (e.g. > 1 month) it may be necessary to cycle
(discharge, then charge) the battery a few times to get full charge capacity. If the A2000 fails to operate reliably from the battery for twenty minutes, battery
replacement is required.
The A-2000 contains an internal Nickel-Metal-Hydride battery. The battery must be
removed by a qualified service technician and disposed of or recycled in
accordance with the national laws of the country. Contact Aspect Medical Systems,
Inc. or the local distributor for a replacement battery.
A burned out fuse usually indicates a serious problem with the electrical system of
the A-2000 unit. Call service before attempting to remove and replace a fuse.
If metal comes in contact with the battery terminals, permanent damage to the
battery and other connecting parts could result.
Do not autoclave the Digital Signal Converter or Monitor. Autoclaving will seriously
damage both components.
Do not submerge.
Do not block fan output. Keep at least three full inches of unobstructed space
between rear of instrument and wall and other instruments. Do not allow other
instruments to block airflow. Do not block ventilation inlet holes on the underside
of monitor.
- 2-3 -
SECTION II SAFETY PRECAUTIONS
Do not open Digital Signal Converter for any reason. The seal to prevent liquids
from entering the Digital Signal Converter may be damaged if opened. Service or
repairs must be performed only by qualified biomedical technicians.
The A-2000 has been designed to operate with a disposable BIS Sensor. The
sensor is a silver/silver chloride electrode array that utilizes Aspect’s patented
Zipprep
electrodes may result in intermittent loss of signal or poor signal quality.
Continuous impedance checking may need to be disabled if the 1 nanoampere 128
Hz impedance check signal interferes with other equipment, e.g., evoked potential
monitors.
VERY IMPORTANT! Use only the Loctite number specified. Using the incorrect
Loctite will damage plastic components.
Use only the parts and tools specified. Use of any others may damage the
instrument.
Failure to position E/L Display screen gasket properly may result in a monitor that
will allow fluid to leak in when the display is cleaned.
Replace battery only with same type of approved battery. Use of non-approved
battery may result in incorrect operation or damage to the monitor.
technology and uses a proprietary connector. Use of incorrect types of
A-2000 is a trademark and Bispectral Index, BIS and Zipprep are registered trademarks
of Aspect Medical Systems, Inc.
- 2-4 -
SECTION II SAFETY PRECAUTIONS
2.2
KEY TO SYMBOLS
ON (power; connection to the mains)
OFF (power; disconnection from the mains)
Audible Alarm Silenced
Operating on Battery
Type BF Equipment
J1
J2
Attention, Consult Accompanying Documents
Attention, J1 RS-232 Serial Port, Consult
Accompanying Documents
Attention, J2 Printer Port, Consult Accompanying
Documents
- 2-5 -
SECTION II SAFETY PRECAUTIONS
Fuse, Replace only with same Type and Rating
Equipotential
Alternating Current
Dangerous Voltage
Protective Earth (ground)
Storage Temperature Limits
- 2-6 -
SECTION III PRINCIPLES OF OPERATION
SECTION III
3.
PRINCIPLES OF OPERATION
The A-2000 BIS Monitoring System consists of:
• The BIS monitor with built-in battery backup and detachable power cord
• The Digital Signal Converter (DSC)
• Aspect’s BIS Sensor Patient Interface Cable (PIC) and BIS Sensor
This section describes the architecture of the A-2000 monitor and DSC and how their
constituent parts interact.
3.1
SYSTEM ARCHITECTURE
Hardware is divided into two main components: the monitor and the digital signal
converter (DSC). The A-2000 monitor contains the circuits for digitally processing the
EEG data, computing the processed parameters, and displaying the waveforms and
processed parameters. The circuits to acquire and digitize the EEG signals reside in the
Digital Signal Converter (DSC).
The monitor also contains the circuits for powering the monitor, DSC, and companion
printer. Integral to these circuits is a battery backup. Printer function is not available
while on battery backup.
A block diagram depicting the monitor subassemblies appears in Figure 3-1. A signal flow
diagram appears in Figure 3-2.
After passing through input protection circuits in the DSC, the EEG signals are differentially
amplified and filtered to remove DC and high frequency components. The signals are
digitized by separate one bit sigma-delta analog to digital converters. The outputs from the
converters are multiplexed onto the DSC communications line and de-multiplexed in the
monitor prior to being fed to the Digital Signal Processor (DSP). The DSP filters the signals
and computes the processed variables. The results are passed to the host CPU for display.
3.1.1
The Digital Signal Converter (DSC)
The DSC contains the inputs, amplifiers, and digitizers for two channels of EEG. It has a
single point connection that connects via a Patient Interface Cable (PIC) to a BIS Sensor.
The A-2000 is designed to process one channel using the BIS Sensor, the A-2000 and DSC
hardware is capable of two channels. The sensor and PIC contains circuits for identifying
them to the monitor. This permits the monitor to configure automatically.
The DSC constantly monitors the combined source impedance at its inputs, and also has
facility for measuring the individual impedance of the channel and ground electrodes. There
are circuits for injecting self-test voltages into the amplifier inputs.
- 3-1 -
SECTION III PRINCIPLES OF OPERATION
Figure 3-1 The A-2000 System Block Diagram
- 3-2 -
SECTION III PRINCIPLES OF OPERATION
Figure 3-2 The A-2000 Signal Flow Diagram
- 3-3 -
SECTION III PRINCIPLES OF OPERATION
3.1.1.1 The DSC’s Preamplifier Board
The preamplifier board contains the input protection circuits, montage mode switches,
differential amplifiers, filter and gain amplifiers, impedance test circuits, self test circuits, and
parts of the sensor ID circuit.
3.1.1.2 DSC Signal Conditioning
The input protection circuits are designed to protect the inputs from destruction by electric
shock from sources such as electrostatic discharge (ESD) or defibrillation. The protection
circuits also reduce the effects of high frequency ambient noise from sources such as
electro-cautery and other devices.
The montage mode switches follow the protection circuits. These switches configure the
inputs appropriately for the sensor. The signals are amplified by instrumentation amplifiers
which have a fixed gain. The amplifiers have DC servos which remove the signals below
high pass cutoff frequency. In the event of amplifier overload, the servos are changed to a
higher frequency to facilitate fast recovery (blocking) under control of the host processor.
Each channel is further amplified to the level required by the A/D converters. The amplifiers
also serve as filters to prevent aliasing by the converters.
3.1.1.3 DSC Impedance Testing
In the default state of the DSC the combined channel electrodes’ impedance is continuously
checked. A small current (approximately 1 nanoampere) is injected into each electrode at
128 Hz, just above the EEG band. The resulting voltages are measured. Equal but opposite
currents are injected into the (+) and (-) electrodes simultaneously while the digital signal
processor measures the resulting voltage. BIS monitoring is performed while combined
impedance is checked.
The DSC can also measure the individual electrode impedance by injecting current into the
REF electrode only. Individual electrode impedance is derived by subtracting the resulting
value from the combined value. BIS monitoring is interrupted while individual impedance is
checked.
The ground electrode impedance is also measured while injecting current into the REF
electrode. BIS monitoring is interrupted while the ground impedance is checked.
The impedance check signal can occasionally interfere with other monitoring equipment
connected to the patient. Evoked potential monitors are particularly susceptible because
they use a wide bandwidth. The automatic impedance check feature can be turned off by
selecting “Impedance Checking – OFF” in the Diagnostics Menu (See Operating Manual for
specific instructions).
- 3-4 -
SECTION III PRINCIPLES OF OPERATION
3.1.1.4 The DSC Communications Board
The communications board contains the analog to digital (A/D) converter for each channel,
the monitor interface, the sensor interface and the power supply circuits. A crystal controlled
DSC master clock is on this board. This clock is the system’s BIS processing clock.
A/D Conversion (Patented technology)
The communications board contains sigma-delta modulators for the two channels. These
run at 16384 samples per second.
Test Signal
A calibrated test signal is generated on the communications board during DSC self test.
The signal is a 2 Hz square wave of approximately +/-50µV. It is applied to the inputs of the
differential amplifiers, resulting in a test of the entire signal path except for the input
connections and protection circuits. During self test noise, gain and frequency response are
checked.
Interface to the Monitor (Patented technology)
The outputs from the two channels are multiplexed in a field programmable gate array
(FPGA). Multiplexed with the EEG data is status information such as DSC identification,
mode (bipolar or referential), lead off indication, and power supply faults. The status
information is only transmitted on command from the host. The output is transformer
coupled onto a balanced twisted pair line. The transformer provides the required patient
isolation.
The communications board decodes the control information coming from the host via a
command line. Commands such as “block” amplifier saturation and conduct impedance
tests are transmitted.
DSC Power Supply (Patented technology)
The DSC derives power from the command line. The line is balanced twisted pair coupled
via a transformer on the communications board. The isolated signal is rectified and linearly
regulated to provide DSC power.
3.1.1.5 The DSC Mechanicals
The DSC is contained in a small custom designed plastic case about the size of a computer
mouse (see Figure 3-3). It is connected to the monitor via a narrow, highly flexible cable.
The case has one large eyelet at the corner to allow the user to use a strap to hang the DSC
or pin it to the bed sheets. The patient connection is accomplished with an Aspect BIS
Sensor for low and balanced impedance. The Patient Interface Cable pigtail and the monitor
cables are strain relieved and permanently attached to the case. A proprietary connector is
used for the patient interface cable connection and a high quality plastic connector is used
for connection to the monitor.
There are no ventilation holes in the DSC case. It will not leak when splashed with liquids.
The case is electrically shielded both to prevent spurious emissions from the DSC and to
prevent externally caused interference with the DSC circuits.
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SECTION III PRINCIPLES OF OPERATION
Cable (PIC)
Monitor
Interface
Cable
DSC - 2
DSC pigtail
Patient Interface
Figure 3-3 The Digital Signal Converter (DSC)
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SECTION III PRINCIPLES OF OPERATION
3.1.2
The A-2000 Monitor
The A-2000 monitor contains the circuits for digitally processing the EEG data, computing
the processed parameters, and displaying the waveforms and processed parameters.
The circuits for acquiring the EEG signal and digitizing them reside in the digital signal
converter (DSC).
The monitor also contains the circuits for powering the monitor, DSC, and companion
printer. Printer function is not available on battery backup.
A block diagram depicting the monitor subassemblies appears in Figure 3-1. A signal flow
diagram appears in Figure 3-2. The signals are acquired and digitized by the DSC. The
DSC multiplexes the signals onto the DSC communications line. The EEG signals are demultiplexed in the monitor and fed to the Digital Signal Processor (DSP). The processor
filters and down-samples them, calculates the processed parameters, and outputs the
data display.
3.1.2.1 The Main Board
The Main board contains the Digital Signal Processors, the Host processor, data memory,
real time clock, and DSC interface.
All software and firmware can be downloaded through the serial port.
3.1.2.2 Digital Signal Processor
The functions of the DSP include: decimation filters for up to 2 channels of EEG data,
computation of processed EEG parameters, control of the DSC, and interface with the
host.
3.1.2.3 Host Processor
The functions of the host processor include: control of the display, interface with the
keypad, serial port, and printer, control of monitor boot up and download, control of
memory.
An on board annunciator is included for generating alarm sounds.
The display interface is a 4-bit LCD type.
The serial port is standard RS-232.
The printer interface is a non-standard serial type with extra lines for printer keys and
printer control and status. It is designed to interface with a Seiko printer interface board.
3.1.2.4 The Digital Signal Converter (DSC) Interface
The DSC interface is composed of two unidirectional bi-phase encoded serial lines, one
going to the DSC and another bringing data from the DSC.
The power to the interface is under software control. An overcurrent detector circuit
monitors current to the DSC. If the current exceeds the expected value, the power is shut
off to the DSC by the hardware, and the DSP is notified.
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SECTION III PRINCIPLES OF OPERATION
3.1.2.5 The Interconnect Board
The A-2000 monitor is designed with a minimum of internal cabling. The Interconnect
board provides the physical mounting and electrical connections for the major
subassemblies of the A-2000. It has mounted to it the power input module (connector for
the AC power cord and associated fuses), the equipotential stud, the power switch, and
connectors for the printer (external), the serial port (external) and the various internal
connectors for the Main PCB, Switch pad, battery, and fan.
3.1.2.6 The Power Supply
The power supply runs from ac power from 100-240 VAC, 50-60 Hz. It provides +5 V (at
6 A) and +12 V (at 0.72 A) outputs and charges the battery (6-cell NiMH) 7.2 V (nominal),
1800 mA. Signals are provided to the processor to indicate AC FAIL, RESET, and LOW
BATTERY.
The power supply switches the rectified AC line at 125 kHz. The output drives the primary
of a step-down transformer that also provides isolation from the ac line. The left side of
the power supply is referenced to AC line and the right side to ground. The transformer
secondary has two outputs which are rectified and filtered to create + 5 V and + 10 V
outputs. The +10 V signal drives a DC-to-DC converter to create the +12 V output and
charges the battery.
The battery driven supply switches the +10 V output at 125 kHz using a pulse width
modulated buck circuit to create the +5 V output. The battery voltage feeds the input of
the same DC-to-DC converter to create the +12 V output.
3.1.2.7 The Battery
The battery is for backup use only. Its life is approximately 5 years or 200 charge and
discharge cycles, whichever occurs first. The battery is a six-cell arrangement including
temperature and current control elements, and has a nominal output of 7.2 volts DC. The
battery is charged only when the A-2000 Monitor is turned on and running from AC power.
It is capable of supporting monitor operation for a minimum of 20 minutes. Printer use is
not enabled during battery operation.
3.1.2.8 The Fan
A fan is located on the rear panel of the chassis. The fan keeps the temperature rise inside
the chassis to within approximately 10 degrees of the ambient temperature.
3.1.3
A-2000 Printer
The printer is fastened to the monitor bottom and is connected mechanically and
electrically (no cable required). The printer interface is compatible only with the optional
A-2000 printer.
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SECTION IV PREPARATION FOR USE AND INSTALLATION
SECTION IV
4.
PREPARATION FOR USE AND INSTALLATION
INTRODUCTION
This section provides installation instructions for the Aspect A-2000 BIS Monitor, Digital
Signal Converter and accessories including:
• Site preparation
• Instrument connections
• Installation and verification procedure
• Repackaging for shipping and storage
4.1
4.1.1
The monitor and its accessories can be stored or shipped within the following
environmental limits. Note that these limits apply to non-operational storage and shipping
situations.
Temperature -20 oC to +60 oC
Humidity 15 % to 95 % (non-condensing)
Pressure 360 mmHg to 800 mmHg
Protect the monitor from sudden temperature changes which can lead to condensation
within the instrument. To minimize condensation, avoid moving the system between
heated buildings and outside storage. Once moved inside, allow the monitor to stabilize
in the unopened shipping container at the inside ambient temperature before unpacking
and placing into service. Before operation, wipe down all visible condensation and allow
the system to reach equilibrium at room temperature.
4.1.2
The A-2000 is not designed for use in areas containing flammable gases or vapors.
Temperature. The Aspect A-2000 Monitor is designed to operate safely at a room
temperature of 5 degrees C to 40 degrees C. Conditions that exceed these limits could
affect reliability.
Humidity. The monitor is designed to operate within specifications at a relative noncondensing humidity of 15% to 95%.
Pressure. The monitor will operate satisfactorily at or above sea level, and is unaffected
by extremes or changes in altitude within atmospheric pressures of 360 mmHg to 800
mmHg.
ENVIRONMENT
Shipping and Storage Environment
Operating Environment
WARNING:
EXPLOSION HAZARD: DO NOT USE THE A-2000 IN A FLAMMABLE
ATMOSPHERE OR WHERE CONCENTRATIONS OF FLAMMABLE
ANESTHETICS MAY OCCUR.
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SECTION IV PREPARATION FOR USE AND INSTALLATION
4.1.3
The A-2000 BIS Monitor requires a power source of 100-240 VAC, 50-60Hz. Current
consumption is 1 ampere maximum (including printer load).
To protect operating personnel and patients, the monitor must be properly grounded.
Accordingly, the monitor is equipped with a hospital grade line cord. The power cord
grounds the system to the power line ground when plugged into an appropriate 3-wire
receptacle.
4.1.4
The compact size of the monitor allows it to be easily installed in most hospital OR
settings without special site preparation. Optional mounting accessories (see Section
2.2.5 of the Operating Manual) are available to secure the monitor to an anesthesia cart
or IV pole, or to allow for secure and stable placement of the monitor on a flat surface.
Power Requirements and System Grounding
WARNING:
FOR PROPER GROUNDING, THE POWER RECEPTACLE MUST BE A
THREE-WIRE GROUNDED OUTLET. A HOSPITAL GRADE OUTLET IS
REQUIRED. NEVER ADAPT THE THREE-PRONG PLUG FROM THE
MONITOR TO FIT A TWO-SLOT OUTLET. IF THE OUTLET HAS ONLY
TWO SLOTS, MAKE SURE THAT IT IS REPLACED WITH A THREE-SLOT
GROUNDED OUTLET BEFORE ATTEMPTING TO OPERATE THE MONITOR.
IF THE INTEGRITY OF THE EXTERNAL PROTECTIVE EARTH GROUND IS
IN DOUBT, THE A-2000 SHALL BE OPERATED FROM ITS INTERNAL
BATTERY POWER SOURCE ONLY.
FOR A-2000s USED OUTSIDE OF NORTH AMERICA: A HARMONIZED LINE
CORD WITH CONDUCTORS HAVING A CROSS SECTIONAL AREA
GREATER THAN 0.75 MM2 MUST BE USED.
Site Preparation
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SECTION IV PREPARATION FOR USE AND INSTALLATION
4.2
Detailed connection instructions are provided in the A-2000 Operating Manual, Section III.
4.2.1
The long flexible cable from the A-2000 Digital Signal Converter connects to the
electrically isolated digital signal converter connector on the front panel of the monitor.
Once connected, the DSC need not be disconnected again. However, if you wish to
disconnect the DSC cable from the monitor, carefully reach as far as possible into the port
opening with your thumb and index finger, squeeze and pull back on the gray cylindrical
connector housing. Do not twist or pull on cord.
4.2.2
The A-2000 is designed to use only 3 - conductor IEC hospital-grade power cords. Check
for a firm connection.
4.2.3
This printer port connector is designed to connect only to the Aspect A-2000 printer for
screen prints. To connect:
1. Turn OFF the monitor.
2. Align the printer connectors located on the bottom of the monitor and top of the printer
3. Secure the printer to the monitor with the mounting screw located in the base of the
4. Turn on the monitor.
INSTRUMENT CONNECTIONS
Digital Signal Converter Connections
Power Cord Connections
Printer Connector
so that they mate correctly.
printer. Use caution not to cross-thread the mounting screw.
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