EnSite System Service Manual Rev 3 V3.2.1 Oct 2002

V3.2.1 Service Manual Index Preface Section 1

Guidelines for Providing and Documenting System Service Field Service Flow Chart General Information

Section 2

Theory of Operation

Section 3

Installation Guide

Section 4

Functional Checkout

Section 5

Field System Calibration

Section 6

Troubleshooting Guide

Section 7

EnSite System Preventive Maintenance

Appendix A 1

Reviewing SYSLOG

2

Freeing up Hard Disk Space

3

UNIX Commands

4

Patient Database Recovery

1

USA Power Quality Requirements

2

60601 Electrical Safety Testing of the EnSite 3000 System

1

2.0 Field Service Computers

2

Flat Panel Display Setup

3

Microcontroller Board Flash EPROM Jumper Setup

1

Isolator Installation

ESI # 85-03159

Appendix B

Appendix C

Appendix D ESI # 85-04124

Forms Field Event Report

ESI # 26-02772

Field Service Report

ESI # 26-02773

Installation Report

ESI # 26-02774

Functional Test Certification

ESI # 26-03637

Preventive Maintenance (P.M.) Report

ESI # 26-04258

PREFACE Guidelines for Providing and Documenting EnSite System Service EnSite System Certification: An EnSite system can be considered “certified” if it is in “as new” condition. “Certified” means the system passes all functional, diagnostic, and calibration tests. The minimum EnSite system components required to be in “certified” condition are: the PIU, BOB, BOB cables, SGI computer, keyboard, mouse, media converter and fiber optic cable, external optical storage drive, ZIP drive, SCSI cables, video cable, and monitor. Since catheter manufacturing processes are written with the expectation that the PIU and BOB are in “certified” condition, error messages other than those listed as allowable in the Functional Test Section of the Service Manual must be evaluated on a case by case basis. If the customer is not using a particular feature of the EnSite system (monitoring Analog, Digital, or ECG channels, for instance), errors that affect only those unused features may not cause the system to be non- functional. However, the system cannot be “certified”, and should be repaired. Generally, most software-reported errors will cause the system to be considered non-functional. After assessing service details outlined by FCE reports, error logs, and direct customer contact, the Service Engineer should arrive on-site fully equipped to handle all necessary repairs. The Service Engineer shall return the EnSite system to “certified” condition. If the engineer cannot complete the required (or requested) repairs, the engineer should inform the customer contact person of when the system will be returned to “certified” condition. If the customer decides not to have necessary repairs completed, make sure to note that system was left in “non-certified” condition in service report.

Warranty Information: See the current EnSite 3000 EP Workstation Assurance Plus Warranty plans for detailed warranty information. Damage due to misuse of product may invalidate warranty repair. If a customer wishes to maintain a system in non-certified condition, be sure the customer is aware that warranty credit for an EnSite catheter showing “too many bad electrodes” will only be issued if analysis shows the catheter has less than 56 good electrodes. Furthermore, FCE case support priority will be lowered.

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Required Levels of Service: Installation System must be left in “certified” condition. Installation is not complete otherwise. Contract / Warranty Service The EnSite system shall be returned to “certified” condition. If the engineer cannot complete the required (or requested) repairs, the engineer should inform the customer contact person of the schedule for completion of system repair. Billed Service The service engineer must completely assess the status of the system. The EnSite system should be returned to “certified” condition. If required repairs are in excess of originally contracted P.O. amount, the customer shall be informed of repairs necessary for the system to be left in “certified” condition. The system shall be repaired to the agreed upon condition.

Instructions for filling out and placing the “Equipment Serviced” label: •

Use “Equipment Serviced” label - ESI part # 49-04284

•

Fill in the day, month and year service was completed on the ‘date’ line.

•

Fill in same month but next year from the “date’ line on the “due” line.

•

Enter your first name’s initial and your full last name on the “by” line.

•

Check all appropriate boxes.

•

Apply label to rear of PIU Electronics chassis above serial number label.

Documentation: Fill out and submit forms per the respective Service Manual section instructions.

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Field Service Flow Chart Tech support receives call and fills out ESI Service Call Information Form, 26-04259

No

Tech Support issues form to Customer Service

Customer Service schedules site visit by FSE

No

Install?

Yes

Section 3 and 4, and Section 5 if necessary

FSE fills out Installation Report Form, 26-02774 and Functional Test Certification, 26-03637

Section 7

FSE fills out PM Report Form, 26-04258 and Functional Test Certification, 26-03637

No

PM?

No Yes

Send both forms to Customer, Customer Service, Tech Support and manufacturing

Customer Service will serve as record repository

All Pass?

Yes

Send both forms to Customer, Customer Service, Tech Support and manufacturing

Customer Service will serve as record repository

All Pass?

Yes

Send both forms to Customer, Customer Service, Tech Support and manufacturing

Customer Service will serve as record repository

All Pass?

No

Yes

No

Repair?

Yes

Troubleshoot as required

FSE fills out Field Service Report, 26-02773 and Functional Test Certification, 26-03637

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85-03997

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Service Manual Section 1

General Information Purpose This section contains background information that is important to know when setting up or servicing the EnSite 3000 System, including Endocardial Solutions’ warranty provisions and service policies, maintenance information, and technical specifications.

Contents Warranty and Service Information...2 EnSite 3000 Assurance Plus Warranty ...2 Assurance Plus Optional Extended Warranty / Service Contract ...2 Service of Equipment Out of Warranty...2 24x7 Telephone Hotline ...2 Hardware Repair...2 Parts and Shipping...2 Cable Replacement...2 Service Loaner ...3 SGI Hardware Repair...3 Software Maintenance Revisions ...3 Software Feature Upgrades...3 Software New Application Releases ...3 System maintenance ...3 Customer performed maintenance...3 Periodic inspection...3 Periodic safety and system calibration tests ...3 Moving the system...4 Technical specifications ...4 Dimensions of major components ...7

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Endocardial Solutions Service Manual

Warranty and Service Information Note: The warranty information provided here is intended for reference purposes. It does not replace the warranty

provided with your system. Furthermore, this warranty information only applies to systems sold directly by Endocardial Solutions Inc.; for systems purchased through a distributor, contact your local distributor for warranty terms and conditions.

EnSite 3000 Assurance Plus Warranty Endocardial Solutions offers a warranty (included with the initial system purchase) for one (1) year, except cables, which carry a 90-day warranty, from the date of installation against defects in material and workmanship with respect to all hardware and software. This includes the Silicon Graphics Workstation, which will be serviced by Silicon Graphics personnel. Endocardial Solutions, Inc., at its option, will either repair or replace defective products. Software maintenance revisions are provided free for a year and feature upgrades are provided at no charge during the first six (6) months after purchase.

Assurance Plus Optional Extended Warranty / Service Contract Endocardial Solutions, Inc. offers extended warranty packages, which provide an extended warranty to begin after one (1) year. The coverage period can be up to two (2) additional years. Contact your Endocardial Solutions representative to receive more information. Beyond the basic coverage for hardware repair and spare parts, the extended warranty options provide an opportunity to receive certain types of software upgrades and new releases at a 20-50% discount.

Service of Equipment Out of Warranty Repairs for systems out of warranty will be billed at the current rate plus parts, shipping and travel expenses if required. Repairs related to the Silicon Graphics Workstation after the first year will be performed by Silicon Graphics personnel and billed at their standard rates. EnSite 3000 EP Workstation loaner systems will be billed at the current rate plus shipping and insurance costs. Refer to EnSite 3000 EP workstation Assurance Plus Warranty plans for current rates.

24x7 Telephone Hotline Your biomedical engineering staff can call our technical service personnel at 1-800-374-8038 option 1. The line is staffed 24 hours a day and can be used for repair consultations, troubleshooting sessions, ordering replacement parts or scheduling service.

Hardware Repair Labor for both on-site and 4off-site repair will be covered under each of the EnSite 3000 Assurance Plus extended warranty programs. This includes the initial service call and subsequent repair visits.

Parts and Shipping The extended warranty coverage packages include free parts replacement and shipping to your facility. Boards will be replaced with new or rebuilt boards of equal or improved quality. Replaced boards become the property of Endocardial Solutions, Inc.

Cable Replacement All cables come with a 90-day warranty after initial installation of the system.

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Section 1: General Information

Service Loaner The extended warranty coverage plans include a service loaner, which will be provided at the customer’s request and at no cost when the system repair will take more than three (3) days. Service loaners are subject to availability.

SGI Hardware Repair Purchase of any of the extended coverage plans will include coverage for repair of the Silicon Graphics workstation. This work will be coordinated through your Endocardial Solutions service contact but will be performed by Silicon Graphics personnel.

Software Maintenance Revisions Revisions to your current software will improve the operation of the software without adding features or changing the user interface. Except for the improved performance, most software revisions will be invisible to the user.

Software Feature Upgrades Upgrades to your current software will improve or add additional features that enhance the usability of the current system. Software upgrades do not add new capabilities.

Software New Application Releases New software releases add additional capabilities to the system. New releases may be accompanied with hardware upgrade requirements. The hardware is not included as part of any discount plan.

System Maintenance Customer Performed Maintenance All surfaces should be cleaned with a dry, lint free cloth gently applied. Where necessary, alcohol may be applied on such a cloth to remove grease and stains. The monitor screens can be cleaned with an appropriate solution. Caution: Do not clean the system components with disinfectants that contain surfactants, such as Cidex Plus. Caution: Absolutely no cleaners should be applied when the system is warm to the touch. Under no circumstances

should the EnSite 3000 System be immersed in liquid or sterilized.

Periodic Inspection The system components should be inspected on a monthly basis: §

Ensure that the fans on system components are operating when power is on.

§

Check the components, cables, and connections for mechanical damage.

§

Verify that inscriptions and labels on the system components are properly and completely fixed.

§

Visually inspect that the instructions for use document is undamaged and complete.

Periodic Safety and System Calibration Tests The Patient Interface Unit and Breakout Box should be tested annually for electrical safety tests and system calibration maintenance checks. These tests require specialized equipment and training. Contact an ESI-trained field service representative to schedule testing. Document Number 85-03997

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Endocardial Solutions Service Manual

Moving the System It is recommended that ESI personnel be present anytime that moving the system requires disassembly. Caution: Do not disconnect any cables other than those mentioned below. These are not user-serviceable

connections.

If the system must be moved, adhere to the following guidelines: 1. Disconnect external equipment from the PIU analog and digital connections. 2. Disconnect any catheters, external stimulator, system reference, ECG electrodes, or unipolar reference connected to the Breakout Box. 3. Disconnect power cords from external power sources. Any cords connected to an isolation transformer secured to a cart may remain connected. 4. Disconnect the fiber-optic cable from the PIU. The Display Work Station (DWS) cart has a hook used for storing the 50 ft fiber-optic cable. 5. For dual monitor systems, disconnect the second monitor’s video cable at the monitor’s video connector. The Display Work Station (DWS) cart has a hook used for storing the 50 ft video cable. 6. Remove the Breakout Box from the patient table and store it on the PIU cart. Note: The Patient Interface Unit (PIU) cart features a bracket for holding the Breakout Box.

7. Secure all cables on the carts to which they are attached. 8. After moving the system, inspect all connections for damage, and reconnect the system. Damaged cables or components must be replaced. Caution: When reconnecting the fiber-optic cable to the PIU, be sure to align the tabbed edge of the cable

connector to the slotted left edge of the jack. 9. Power ON the system.

Technical Specifications Patient Interface Unit specifications Safety Leakage

Conforms with IEC 601-1, Class 1

Protection

Conforms to IEC 601-2-27

Isolation

> 4000 volts; > 5000 volts surge

Protection against the ingressIPX0 of water Input from patient ECG

12 lead

Catheter electrodes

2 mm pin jacks (16 pairs)

EnGuide signal

5.6 kHz signal routed to the EP catheter electrodes

EnSite® Catheter

Custom cable assembly

Input from other equipment Analog inputs

8 standard high level analog inputs (± 10 V)

Digital inputs

8 CMOS digital inputs (0 to 5 V)

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Section 1: General Information

Signal processing specifications Sampling rate

1200 Hz

Resolution

12 bit A/D

Gain accuracy:

± 2%

Full scale input range

adjustable from ±1.6 mV to ±0.125 V

Input signal DC offset

± 500 mV

Display workstation specifications Octane workstation

Silicon Graphics, Inc.

Optical disk drive

Magneto-optical media drive

®

Zip drive

Iomega Corporation

Display monitor

21" diagonal monitor(s). Refer to the product literature provided with the monitor for connector characteristics.

Software specifications Operating system

Irix 6.x

Mapping system

Endocardial Solutions, Inc. proprietary software; version 3.X, PrecisionT M

AC/MAINS power input specifications Input voltage

110/120 V or 220/240 V

Input frequency

50/60 Hz

Power inputs (nominal) DWS components

750 W maximum

PIU

300 W maximum

Patient interface monitor

120 W

Mode of operation

Continuous

Environmental conditions Operating

+18 to +35 °C to 90% relative humidity, non-condensing

Transport/storage

-25 to +60 °C to 90% relative humidity, non-condensing

System component physical characteristics Component

Dimension in cm (nominal)

Weight in kg (lb.)

Patient Interface Unit (PIU)

66 H, 59 W, 48 D

68 (150)

Breakout Box

31 H, 34 W, 12 D

5.5 (12)

Workstation

42 H, 48 W, 48 D

28 (60)

Monitors

51 H, 48 W, 48 D

30 (65)

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Endocardial Solutions Service Manual Applicable standards IEC 601-1: 1988 including A1:1981 and A2:1995

Part 1. General requirements for safety

EN 601-1-1: 1990 including A1:1993 and A2:1995

Part 1. Collateral standards: Safety requirements for medical electrical systems

IEC 601-1-2: 1993

Part 1. General requirements for safety Part 2. Collateral standard: electromagnetic compatibility - requirements and tests

ANSI/AAMI ES1-1985

American National Standards Institution’s Safe Current Limits for Electromedical Apparatus standard

EN 55011, Group 1, Class A, 1991.

Electromagnetic compatibility requirements of European Standard

CISPR 11, Group 1, Class A: 1990 EN60601-1-2: 1993

Immunity requirements of European Standard

IEC801-2: 1991

Electrostatic discharge requirements

IEC 801-4: 1988

Electrical fast transient/burst requirements

UL 544

Medical and dental equipment

Software Version 3.0 Hot key shortcuts Key

Function

F2

Save event marker

F3

Save bookmark

F4

Record/Stop/Complete

F6

Lesion on EnGuide

F8

Saturation recovery

F9

Reset offsets

← (or F11 for maintain user)

Step backward 1 sample

→ (or F12 for maintain user)

Step forward 1 sample

Space bar

Scroll selected button

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Section 1: General Information

Dimensions of Major Components Display Workstation (DWS) with Cart

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Endocardial Solutions Service Manual Patient Interface Unit (PIU) with Cart

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Section 1: General Information Octane (DWS Computer)

Patient Interface Unit

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Endocardial Solutions Service Manual Monitor

Breakout Box (BOB)

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Service Manual Section 2

Theory of Operation Purpose This document is intended to provide the reader with a general understanding of the technology behind the EnSite 3000 System.

Contents Purpose of the PIU...2 Requirements affecting the PIU design ...2 Description of EnSite 3000 System use during an EP procedure ...3 ESI 3000 PIU Functional Block Diagram ...3 Signal Conditioning...3 The EnGuide Signal...6 Electrical Safety ...7 Patient/User Shock Protection...7 Defibrillation Protection...8 Care of Equipment to Maintain Safety ...8 Major Assemblies ...9 Electronics Chassis...9 Power Supply Chassis...11 Breakout Box...12

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Endocardial Solutions Service Manual

Purpose of the PIU The PIU has two major functions when used during an EP procedure: receiving and conditioning the bio signals from the sensors (for example the EnSite catheter) and generating the EnGuide signal for use in locating contact catheters in the chamber of the heart in which the EnSite resides.

Requirements affecting the PIU design The primary requirements affecting the PIU design were determined from the basic functional requirements dictated by the types of data to be taken as well as lessons learned from the first generation of the electronics. The final requirement list was winnowed to include these: §

Safety: meet or exceed UL, IEC, CSA, and AAMI standards for AC mains isolation and auxiliary patient electrical currents.

§

Meet or exceed FCC, IEC, CSA standards for EMI/RFI and RF immunity.

§

Input signals: Signal type

Number of Channels

Input Range

Bandpass

EnSite Bio

64

1.6mV -125mV

0.1Hz-300Hz

EnSite Ring Bio

2

1.6mV -125mV

0.1Hz-300Hz

Contact Catheter

16 (unipolar/ bipolar)

1.6mV -125mV

0.1Hz-300Hz

ECG

12

1.6mV -125mV

0.1Hz-300Hz

Impedance

64

80Ω max

1KHz-20KHz

Analog

8

100mV -10V

DC-300Hz

Marker

8

TTL compatible

Line power monitor

1

N/A

Set by sample rate N/A

§

Use off-the-shelf parts wherever available.

§ §

All data to be a minimum of 12 bits of resolution. Simultaneous sampling of all signals at a rate of at least 600s/s.

§ §

Appropriate defibrillator protection on all patient applied signal inputs. Capability for locating multiple catheter rings.

§ §

User selectable bio signal reference (either EnSite catheter ring E3 or a reference supplied from another EP catheter). User selectable contact catheter unipolar/bipolar sensing.

§ §

User controllable amplifier saturation recovery. User controllable pace blanking.

§ § §

Communication with the control computer via 10MB/s ethernet fiber optic cable. BIT and BIST hardware and software. High rejection of 50/60Hz power line frequencies.

§ § §

All PIU functions controllable via commands on the ethernet link. No mechanically adjustable components on circuit cards. Ability to simultaneously process configuration commands while collecting real-time data.

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Section 2: Theory of Operation This list of requirements only includes those that are visible and important from a user perspective; many more were defined that dealt with fundamental design issues and system operation that are invisible to anyone looking from the outside in. The requirement that had the largest effect on the system design was the total number of channels of data that needed collection. This required a large amount of circuitry because we could not afford to design the analog ASICs needed to shrink the circuit mass. The circuit mass then dictated the amount of patient-safe DC power that would be needed to power it. We iterated several times between the circuitry requirements and the maximum available DC power, trading off component and system performance for low power consumption, and finally converging on a design that gave acceptable signal performance that was still well within the available power budget.

Description of EnSite 3000 System use during an EP procedure ESI 3000 PIU Functional Block Diagram

Signal Conditioning Defibrillator Protection

All patient connected signals (with the sole exception of the stimulator signals) entering the Breakout Box first go through a defibrillator protection network consisting of series connected resistors and a diode clamp circuit. This is designed to dissipate the defibrillator energy and clamp the electronic components’ inputs and outputs to safe operating voltages. The values of the resistors have been selected to provide a compromise between noise (primarily Johnson noise and that produced by input impedance mismatch upsetting CMRR) which would demand low value resistors and shunting too much defibrillator energy from the patient through the electronics, which would demand high value resistors.

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Endocardial Solutions Service Manual Function of SYS REF and the “Belly Patch”

Unlike most other biomedical instrumentation, the PIU requires the use of a low impedance connection between the PIU power supply common and the patient to reduce the effect of mains (50Hz or 60Hz) noise on the sensed signals. The reason for this is that most biomedical instruments either measure signals from closely spaced electrodes (bipolar measurements on most EP systems) or drive the patient with a signal that reduces the effects of mains noise (drive reference on ECG systems). Bipolar measurements reduce mains noise because the measurement dipole is so small that the mains noise induced on both electrodes of the pair is almost the same amplitude and phase resulting in a very small common mode output from the sense amp. ECG systems handle this a little differently. ECG systems actually measure the mains noise on one set of leads and then drive the patient with an out-of-phase replica of this signal to servo out the mains noise contribution. The EnSite system requires that we measure signals with respect to a reference (either ring E3 or the ring on another catheter) that may be located a large distance from the EnSite electrodes. Also the source impedance of the EnSite electrodes is much larger and much more variable than the reference electrode impedance. Add to this the fact that we must measure biological signals in the range of DC to 300Hz as well as impedance signals at 5600Hz, and you can see that the CMRR of the amplifiers is very seriously affected with a concomitant increase in mains noise. One way of avoiding this problem is to provide an isopotential between the patient and the PIU electronics. We do this by placing a low impedance patch (an “R2” patch or equivalent) on the patient’s abdomen and then connecting it to the PIU power supply common. In effect we cause the mains component to be the same (or very similar) on both the patient and on the PIU power supply common. This has the effect of making what was a differential mains signal a common mode signal and so eliminating it. The main disadvantage is that one must be very careful to minimize bias or other currents. Another disadvantage is that it requires care in design and layout of the defibrillator protection circuitry to prevent large circulating currents when the patient is defibrillated. Also this only works because the PIU is well isolated from earth ground and so the power supply common does not pose a hazard to the patient. EnSite Signals

The electrical portion of the EnSite catheter consists of a hollow cylindrical braid of 64 polyimid covered stainless steel wires with one laser ablated electrode on each wire. The EnSite catheter also has three rings labeled E1, E2, and E3 whose use will be describe in the succeeding sections. When the EnSite catheter is inserted into one of the four chambers of the heart and deployed the electrode array is distributed in a regular pattern across the surface of a prolate ellipsoid of revolution. The electrodes make galvanic contact with the blood and sense the electrical potentials induced upon them by the electrical fields generated by myocardial activity. The sensed signals can be on the order of tens of microvolts for non-contact mid-diastolic potentials to several millivolts for contact potentials if an EnSite electrode happens to come in contact with the endocardium. Since, by definition, a potential must be measured with respect to some reference, the electronics have provision for using either the EnSite E3 electrode or the UNI REF jack on the Breakout Box as the signal reference for the Breakout Box amplifiers. Usually E3 used when the EnSite is in the heart. In situations where the E3 electrode is unavailable (for instance in a jugular approach) the UNI REF jack can be used as the reference. Using UNI REF requires that an EP catheter ring be available and that the ring be in a stable spatial position with respect to the EnSite array. If the EnSite array and reference move with respect to one another it will cause succeeding data to be suspect. The selection between E3 and UNI REF is commanded via the DWS software and is physically accomplished via analog switches in the Breakout Box. The selected reference is buffered by a unity gain operational amplifier and then distributed to the inverting inputs of the instrumentation amplifiers in the Breakout Box. Each of the EnSite electrodes is DC coupled to its individual instrumentation amplifier non-inverting input. Instrumentation amplifiers were chosen so as to provide the best common mode rejection at 50/60Hz. As stated above the selected unipolar reference is connected to the inverting input. The gain of the input instrumentation amplifier is fixed at 5. This gain was selected as a compromise between setting the noise figure of the Breakout Box (demanding higher initial gain), the available power supply rails (±8V), and the half-cell potentials of the electrodes (both demanding lower gain). The half-cell potentials are produced by the differing valences of the stainless steel in the rings and the electrodes. In a battery, when two different metals are separated in an electrolyte a potential is Document Number 85-03997

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Section 2: Theory of Operation developed between the metals. The same thing happens in the body with the blood acting as the electrolyte. The gain of the amplifiers must be low enough so that the half-cell potentials do not cause them to saturate. With a gain of 5, the half-cell potential can be as high as 1V and the instrumentation amplifiers won’t saturate. In addition to the 64 array electrode signals, the bio signals from EnSite rings E1 and E2 are buffered and amplified. These signals are used to provide sensed potentials at the ellipsoid poles where there are no array electrodes. The low impedance and buffered signals are then routed from the Breakout Box to the PIU electronics chassis. Each EnSite signal is routed to one of four Bio boards and one of four Impedance DeModulator (IDM) boards (see The EnGuide Signal below) for further processing. The Bio board accepts the EnSite signal, buffers and filters it (0.1Hz to 300Hz) and applies it to an A/D converter. The 0.1Hz highpass pole is set to block the DC half-cell voltages from the succeeding gain stages and the 300Hz lowpass reduces the noise bandwidth and provides anti-aliasing for the A/D converter. A detailed description of the Bio board operation is given later in this document. The E1 and E2 ring bio signals are sent to the Bio board that amplifies the ECG signals. This board is electrically identical to the EnSite Bio boards. Once the signal is digitized, it is passed across the digital backplane to the Microcontroller board where the data is buffered and then sent to the DWS via the ethernet connection. The digital backplane is also used to send configuration commands to the Bio board that set gains, saturation recovery, and test modes. Contact Catheter Signals

The contact catheter signals are, like the EnSite signals, also bio signals. The contact catheter channels are used to sense signals from standard EP catheters that are introduced into a chamber of interest (not necessarily the same chamber as the EnSite catheter). In a conventional EP study, electrical potentials of the endocardium are usually determined by measuring the potential between closely spaced pairs of electrodes: a bipolar measurement. Bipolar measurements are popular because they inherently yield information on the direction the depolarization wavefront is propagating, they reject mains noise, and they are free of “far field effects.” The “far field effect” is the sensing of electrical potentials generated far from the site of interest. Its main disadvantage is that the electrodes must be in contact with tissue to make these measurements. Since EP physicians are accustomed to using bipolar measurements, these must be provided. The other means of measurement, unipolar measurement, uses a reference electrode located “far” away from the measurement electrode. The major problem with this type of measurement is that is more easily corrupted by mains noise because the measurement dipole is so large, but conversely you need not be in contact with tissue to make the measurement. One of the reasons for the need to have the catheter channels measure unipolar potentials is that the EnSite catheter makes unipolar measurements. As a result, if you wish to compare reconstructed (“virtual”) electrograms with sensed electrograms, they need to be made using the same method. Since the EnSite catheter must by its very nature make unipolar measurements, the catheter channels were designed to allow unipolar measurements as well. In any case, the selection of bipolar mode is made on a channel by channel basis by configuring analog switches that select a specific pin jack for input to the catheter channel amplifier inverting input. Unipolar measurements are made the same way except the inverting input of the catheter channel amplifier is connected to the same reference as that selected for the EnSite catheter using the same switch as used for bipolar mode. The catheter channel gain is fixed at 5 for the same reasons as the EnSite gains. The catheter signals are then routed from the Breakout Box to the PIU electronics chassis “Catheter Amplifier” board. This board is electrically identical to an EnSite Bio board.

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Revision 03

Document Number 85-03997

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