SIU5 Users Manual Ver B

© COPYRIGHT 2007

ASTRO-MED, INC.

This manual is copyrighted with all rights reserved. No part of this manual may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any language in any form by any means without written permission of Grass Technologies, An Astro-Med, Inc. Product Group. Information in this document is subject to change without notice. Astro-Med, Inc. assumes no responsibility for any errors, omissions or inaccuracies whatsoever.

TRADEMARKS AURA®, Aurora®, Beehive®, Brain Navigator®, BrainTree®, Comet®, EZM®, EC2®, FASS®, Gamma®, GrassLab®, Heritage®, H2O®, Panorama®, PolyVIEW®, SAFELEAD®, SleepTrek®, Sonoma®, SzAC®, TWin® and TWinLOOK® are trademarks of Astro-Med, Inc. Other brand and product names are trademarks or registered trademarks of their representative holders.

STIMULUS ISOLATION UNIT IDENTIFICATION DATA Congratulations. Your Grass purchase is an investment in the finest of state-of-the-art medical technology. The information provided below lists the model number and serial number of your Stimulus Isolation Unit. If, for any reason, it should be necessary for you to contact Astro–Med, Inc. regarding your purchase, please refer to the following: Model Number:______________________ Serial Number:______________________

Printed in the United States of America

IMPORTANT This manual is subject to periodic review, update, and revision. Customers are cautioned to verify that the manual’s information applies to the software and hardware present in the equipment. This product performs as described in this manual, and in accompanying labels and/or inserts, when assembled, operated, maintained, and repaired in accordance with the instructions provided. This product must be cleaned and checked periodically. Do not use a defective product. Parts that are broken, missing, worn, or contaminated should be replaced immediately. If repair or replacement becomes necessary, call or write to request service advice from Grass. This product must not be altered without the prior written approval of Grass. The user of this product shall have the sole responsibility for any malfunction that results from improper use, faulty maintenance, improper repair, unauthorized service, or alteration by anyone other than Grass. The safety, reliability, and performance of this device can only be assured under the following conditions: • If the device has been used according to the accompanying operating instructions. • If changes or repairs have been carried out by Grass. • If it is used in buildings having ground equalization wiring that complies with relevant UL, CSA, IEC or other local standards and regulations.

INTENDED USE For converting the nonisolated output of Grass Model S44, S48, S88, S11 and S8800 Stimulators to isolated constant voltage. FOR USE BY QUALIFIED PERSONS ONLY. NOT INTENDED FOR THERAPEUTIC PURPOSES.

WARNINGS READ THIS BEFORE OPERATING The output voltage and available current of this Stimulus Isolation Unit when coupled to Grass Stimulators, is large enough to be lethal or cause burns particularly with long durations and high current settings. The state of the art is such that the potential danger to human and animal subjects from sustained stimulation even at low levels is still not completely understood. Grass Stimulator Models S9 and SD9 have built-in ground isolation circuits. All other Grass Stimulators should be used in conjunction with Grass Stimulus Isolation Units to reduce the effects of ground leakage currents. Grass Technologies, An Astro-Med, Inc. Product Group waives any responsibility whatsoever for any injuries incurred to the operator of this instrument or to any animal or human subject as a result of the improper use or abuse of this Stimulator.

Table of Contents 1. SPECIFICATIONS ... 1-1 2. INTRODUCTION ... 2-1 DESCRIPTION ... 2-1 DESIGN & PRINCIPLE OF OPERATION ... 2-2 3. STIMULUS ARTIFACT ... 3-1 WHAT IS STIMULUS ARTIFACT? ... 3-1 SOURCES & REDUCTION OF STIMULUS ARTIFACTS ... 3-2 4. CONNECTION OF THE SIU5 TO THE STIMULATOR ... 4-1 POWER FOR SIU5 OPERATION ... 4-1 CONNECTION OF THE SIU5 TO THE GRASS MODEL S44, S48, S88, S11 OR S8800 STIMULATORS ... 4-2 5. OPERATION OF THE SIU5 ... 5-1 OPERATION OF THE SIU5 ... 5-1 COUPLING ... 5-1 POLARITY ... 5-2 MULTIPLY INPUT VOLTS BY SWITCH ... 5-2 6. APPLICATIONS ... 6-1 USE OF CRO WITH THE SIU5 TO MEASURE STIMULUS VOLTS & CURRENT ... 6-1 MIXING THE OUTPUT OF STIMULATORS THROUGH TWO SIU5S TO GET TRUE ADDITION AND/OR BIPHASIC WAVEFORM ... 6-3 STIMULUS ISOLATION WITH TRAINS, PAIRS, REPETITIVE OR SINGLE PULSES ... 6-4 MONITORING LARGE DC CURRENTS WHILE MAINTAINING STIMULUS ISOLATION ... 6-4 SIU5 WITH GRASS CCU1 CONSTANT CURRENT UNIT ... 6-5 USE OF THE SIU5 WITH OTHER THAN GRASS STIMULATORS ... 6-6

SIU5 Stimulus Isolation Unit

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7. TROUBLESHOOOTING ... 7-1 TROUBLESHOOTING ... 7-1 SERVICE POLICY WARRANTY

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Table of Contents

1

Specifications

Isolation _______________ 2 MHz Transformer Input __________________ Compatible with Grass S44, S48, S88, S11 or S8800 Stimulators Common Mode Voltage __ Including RF is reduced approximately 10 to 40 times over the range of 15 to 150 V, and 100 times over the range from 0.015 to 15 V Output Impedance _______ Approximately 1,000 Ω with all Stimulators. Combined with the Grass Model CCU1 Constant Current Unit, a constant stimulating current isolated from ground is obtained. Output Impedance to Ground ______________ Capacitive: balanced 25 pF to each output terminal. Conductive: greater than 1012 Ω. Output Waveform _______ Square waves of Grass Stimulators are reproduced with negligible change on direct-coupled (monophasic) operation. Capacity-coupled operation can be selected by means of a switch. Constant Voltage Ranges _ 0.015 to 150 V in 3 decade ranges Polarity ________________ Reversible by a switch. No ground reference. Power _________________ Powered by stimulus pulses – no additional power source is required. Minimum power is required from stimulator to drive the SIU5 and thus reduces stimulus artifact to a minimum. Physical Size ___________ 2.5" x 3" x 7" (6.4 cm x 7.6 cm x 17.8 cm) Weight: 2-1/2 lbs. (1.1 kg) (All specifications subject to change without notice.)

SIU5 Stimulus Isolation Unit

1-1

1-2

Chapter 1 Specifications

2

Introduction

Description Use the Model SIU5 between a Grass Stimulator and the stimulating electrodes to minimize artifact. Excessive stimulus artifact tends to block recording instruments, often obscuring the recording of the response. Isolation of the stimulus signal from ground reference reduces the ground current between stimulating and recording systems (the primary source of stimulus artifact) and provides greater safety for direct human and animal stimulation. The SIU5 outputs can be connected in series so that stimulus voltage from various sources can be mixed even with the opposite polarities and introduced through a common pair of electrodes. One SIU5 will then be necessary for each stimulus output. The SIU5 contains a radio frequency (RF) oscillator which is modulated by the Stimulator output. The oscillator is electromagnetically coupled via an RF transformer to a secondary coil whose impedance is balanced to ground at stimulus frequencies. The secondary voltage is demodulated by diodes and the RF filtered. Finally, the signal size is controlled by a decade attenuator. Input and output waveform are essentially identical, but the output voltage is nearly independent of ground. The output is not directly linear with input.

SIU5 Stimulus Isolation Unit

2-1

DESIGN & PRINCIPLE OF OPERATION The Grass SIU5 Stimulus Isolation Unit is a transistorized radio frequency circuit designed to be connected in series with the output of a S44, S48, S88, S11, S8800 and other similar Stimulators and stimulating electrodes to isolate the stimulus from ground, thus reducing stimulus artifact. The carrier frequency of the oscillator in the SIU5 is modulated by the output voltage of the stimulator. The secondary coil of the SIU5 is isolated from ground. At this point, the signal is rectified and demodulated to reproduce the original stimulator square wave form. A multi-position decade attenuator, a polarity switch and direct-coupled, capacity-coupled switch are included on the front panel. See Figure 2-1. The SIU5 is driven directly by the stimulator output (150 volts maximum) and does not require any additional power source.

RFC

Out

RF Oscillator

From Stimulator

Demodulator

Coupling

or

Polarity

Multiplier

or

No Ground

Figure 2-1: Simplified SIU5 Circuit

2-2

Chapter 2 Introduction

3

Stimulus Artifact

What is Stimulus Artifact? When a stimulus pulse is introduced to a preparation to evoke a response, an electrical artifact appears in the recording instrumentation as the result of the speed of the stimulus current to the recording electrodes. This artifact precedes the evoked response in time as indicated in the CRO record of Figure 3-1. The delay between stimulus artifact and the evoked response is dependent upon stimulation parameters and the characteristic properties of the preparation.

Stimulus Artifact Response ms

Figure 3-1: Stimulus Artifact

Some stimulus artifact is desirable to establish the time of stimulation. However, excessive stimulus artifact may obliterate the display of the desired response as is often the case when small evoked potentials are sought after a stimulus pulse of excessive amplitude or duration.

SIU5 Stimulus Isolation Unit

3-1

SOURCES & REDUCTION OF STIMULUS ARTIFACTS Excessive stimulus artifact results when the recording electrodes unavoidably measure the field of distribution of the stimulus voltage through the preparation. The size of the stimulus and proximity of the recording and stimulating electrode pairs contribute to the artifact amplitude. See Figure 3-2.

S

S

Equipotential stimulus voltage lines

R R

S = Stimulating Electrodes R = Recording Electrodes

Stimulus Current Flow

Figure 3-2: Stimulus Voltage Field Distribution

Note: For optimum recording results, use independent stimulating and recording electrodes and keep recording electrodes perpendicular to stimulus current flow, if possible.

To alleviate stimulus artifact: 1.

2.

3.

3-2

Isolate the stimulus pulse from ground and thereby reduce the circulating ground currents between the stimulator, preparation and recording instrument. Space stimulating and recording electrodes as far from each other as possible and position them for maximum cancellation of field effects. Use as small a stimulator pulse with as short a duration as is possible (approximately 0.1 milliseconds).

Chapter 3 Stimulus Artifact

If the field distribution pattern of stimulus current causes substantial stimulus voltage between the recording electrodes, the resulting artifact cannot be avoided. The use of series resistors can create a constant current rather than a constant voltage source independent of changes in electrode impedance. Connect resistors in series with both output terminals of the SIU5 The magnitude of the resistors should be at least five times that of the electrode impedance. The characteristics of the SIU5 permit the shielding of stimulating and recording electrodes leads, thus reducing the capacitive coupling between recording and stimulating leads. (See Figure 3-3.) Shield if desirable

Stimulator

SIU5

Amplifier

Preparation

Shielded Stimulating Leads

Recording Leads

Figure 3-3: Sheilding Electrode Leads

SIU5 Stimulus Isolation Unit

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3-4

Chapter 3 Stimulus Artifact

4

Connection of the SIU5 to the Stimulator

Power for SIU5 Operation The SIU5 receives power for operation from the stimulus. No additional power source is required. Each SIU5 is coupled to the front of its companion stimulator with a cable provided which is specific for each model stimulator. See Figure 4-1. On all Grass Stimulators, it is necessary to set the VOLTS multiplier switch to the X10 or X1 positions. See CHAPTER 5, MULTIPLY INPUT VOLTS BY SWITCH. Note: Never connect a ground to either of the output terminals of the SIU5 when stimulating. To do so would defeat the purpose of stimulus isolation.

The maximum power output obtainable from the SIU5, when driven with a S44, S48, S88, S11, or S8800 Stimulator, is approximately 5 watts when the total impedance measured at the electrodes is equal to the output impedance of the SIU5 (1000 Ω).

SIU5 Stimulus Isolation Unit

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CONNECTION OF THE SIU5 TO THE GRASS MODEL S44, S48, S88, S11 OR S8800 STIMULATORS Connect one of the connectors on the cable provided to the output on the front of the Stimulator and the other connector to the SIU5 input. There are two outputs on the S88, S11 and S8800 (S1 and S2); therefore, two SIU5s are required to isolate both outputs. See CHAPTER 6, STIMULUS ISOLATION WITH TRAINS, PAIRS, REPITITIVE OR SINGLE PULSES. Set the Stimulator VOLTS multiplier switch according to the suggestions in CHAPTER 5, MULTIPLY INPUT VOLTS BY SWITCH.

Stimulator

SIU5

Figure 4-1: Connection of the SIU5 to the Stimulator

4-2

Chapter 4 Connetion of the SIU5 to the Stimulator

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Operation of the SIU5

Operation of the SIU5 COUPLING Direct Coupled: When the COUPLING switch is in the DIRECT position, a DC output voltage is sustained for a DC input voltage and the monophasic square wave from the stimulator is preserved. Capacity Coupled: When the COUPLING switch is in the CAPACITY position, a capacitor is introduced in series with the output. A biphasic pulse appears at the output. The effective energy of the negative and positive components of the pulse are equal in coulombs, if they are averaged over a sufficiently long period of time. Each component does not necessarily possess the same peak voltage or current.

COUPLING DIRECT

CAPACITY

Electrode polarization caused by an unequal discharge of current in one direction in preference to another (e.g., DC) results in an unequal migration of ions to and from the electrode. This condition is minimized by the equal negative and positive components of a biphasic wave. Biphasic stimulation is preferred, particularly during long-term electrode implants or short pulse stimulation, to reduce the formation of gas bubbles and toxic electrolytic deposits.

SIU5 Stimulus Isolation Unit

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POLARITY The POLARITY switch determines the polarity of the SIU5 output, independent of a ground reference, providing no grounds have been attached to the stimulating electrodes or their leads. In the NORM (normal) position, the red OUT terminal is positive with respect to the negative black OUT terminal. In the REV (reverse) position, the black OUT terminal is positive with respect to the negative red OUT terminal.

POLARITY NORM.

REV.

MULTIPLY INPUT VOLTS BY SWITCH The MULTIPLY INPUT VOLTS BY switch is intended to permit gross attenuation of the stimulus voltage delivered to the preparation. Since the SIU5 is designed to be placed close to the preparation, this switch is in a convenient location. The VOLTS dial on the stimulator may be used as the “fine” stimulus voltage control.

MULTIPLY INPUT VOLTS BY X.01

X.1

X1

To obtain minimum stimulus artifact, use the minimum voltage possible from the stimulator, and adjust for maximum output voltage on the SIU5. The minimum input voltage required to produce a 1:1 relationship in output voltage is approximately 10 volts (1.5 volts in older models). For stimulation procedures requiring low voltages, set the stimulator VOLTS multiplier to the X10(SIU) position and set the SIU5 MULTIPLY INPUT VOLTS BY switch to the X0.1 position to divide the stimulus voltage by 10 times. The following chart lists preferred SIU5 and stimulator settings for various SIU5 output voltage ranges. “Fine” control of voltage is made using the VOLTS dial on the stimulator. Stimulus Volts required from SIU5 15 to 150 1.5 to 15 0.15 to 1.5 0.015 to 0.15

Stimulator Range Switch X10(SIU) X10(SIU) X10(SIU) X1

SIU5 Range Switch X1 X0.1 X0.01 X0.01

Figure 5-1: Preferred SIU5/Stimulator Settings for Output Voltage Ranges

5-2

Chapter 5 Operation of the SIU5

The relationship between the stimulator VOLTS dial and the SIU5 open circuit voltage is not linear. The Stimulus Isolation Units are factory adjusted so that the VOLTS dial on the stimulator reads the correct value at the high end of the scale with open circuit at the SIU5 output. The voltage setting on any stimulator is not an accurate indication of the output voltage or current. The voltage or current at the output will vary with the load. For precise current or voltage measurements, monitor the output with a CRO, See CHAPTER 6, USE OF CRO WITH THE SIU5 TO MEASURE STIMULUS VOLTS & CURRENT.

SIU5 Stimulus Isolation Unit

5-3

5-4

Chapter 5 Operation of the SIU5