A-MSystems 1800 User manual

INSTRUCTION MANUAL
FOR
MICROELECTRODE AC AMPLIFIER
MODEL 1800
Serial #__________
Date____________
A-M Systems, Inc.
PO Box 850
Carlsborg, WA 98324
U.S.A.
360-683-8300 800-426-1306
FAX: [phone]
http://www.a-msystems.com
Version 7.0
Febrary 2002

NOTE
This instrument is not intended for clinical measurements using human
subjects. A-M Systems, Inc. does not assume responsibility for injury or
damage due to the misuse of this instrument.
Contents
General Description ............................................................................................................................ 1
Instrument Features ............................................................................................................................................ 1
Controls and Connectors .................................................................................................................................... 2
Operating Instructions ....................................................................................................................... 4
Typical Set-Up Procedure ................................................................................................................................... 4
Problem Solving ................................................................................................................................................. 6
Theory of Operation ........................................................................................................................... 9
Overview ............................................................................................................................................................ 9
Operational Modes ........................................................................................................................................... 10
Component Modules ......................................................................................................................................... 12
Calibration Proceedures .................................................................................................................. 13
Specifications..................................................................................................................................... 18
Warranty and Service ...................................................................................................................... 19
Each Microelectrode Amplifier
is delivered complete with:
Two Head Stage with 5 Foot Cables
Six 4 Inch Electrode Connector Cables
Rack Mount Hardware
Instructions & Maintenance Manual

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
1
General Description
Instrument Features
The AC Microelectrode Amplifier Model 1800
is a two-channel, differential amplifier with
headstage probes. The instrument is intended
for extracellular recording and/or stimulating in
conjunction with high impedance metal
microelectrodes. It can be used in a number of
research or teaching applications requiring
extracellular neurophysiological recording from
excitable tissue, such as nerve, muscle (EMG), EEG,
EKG, and ERG recordings. The instrument is not
intended for clinical measurements using
humans.
Each channel of the Model 1800 contains a high-gain, low-noise differential amplifier
stage followed by low frequency, high-frequency, and notch filters. Three operating modes
are available to accomodate recording, stimulating, and verification of electrode
impedance. Record Mode offers three levels of signal gain (x100, x1000, x10 000).
Stimulus Mode allows the current passing through the electrode to be measured during
stimulation. Impedance Mode utilizes an internally calibrated current source to allow in
situ verification of electrode impedance.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com 2
Controls and Connectors
INPUT: This 9-pin connector receives the signal from the
Headstage Probe for further processing.
STIMULUS: This 5-pin connector enables an isolated stimulus
source to be utilized to pass current through the electrode
while the channel is in Stimulate Mode. The pin assignments
are listed in the following table.
Pin Location Signal
Aupper left +
Bupper right -
Hmiddle ground
HEADSTAGE PROBE: The Headstage Probe has three sockets
and comes with three wires that will connect these sockets to
standard electode pins. PROBE+ is used to connect to the
electrode (usually an high impedance metal electrode).
PROBE- is used to connect to the indifferent lead. Either the
PROBE GND connector or the front panel GND must be
connected for proper operation. Usually the PROBE GND
connector is tied to the indifferent lead. If you desire to have
the current constrained to a known path you may want to
place the GND elsewhere. Actual GND placement depends on the application.
MODE: This rotary switch controls the operating mode for its
channel. The switch allows the user to select Record Mode
(REC) Stimulate Mode (STIM), or Impedance Check Mode
(IMP).
GAIN: This rotary switch controls the level of signal gain for its
channel while the channel is in Record Mode. The switch
allows the user to select from X100, X1000, or X10 000 gain.
This switch has no effect in Stimulate Mode and Impedance Check Mode.
CAPACITY COMP: This knob provides control over the amount of
capacitance in parallel with the electrode while the channel is in
Impedance Check Mode. Turning this knob clockwise decreases the level
of capacitance. With the electrode capacitance reduced, the measured
impedance will largely be a measure of the resistive component of the
electrode. Warning: Turning the Capacity Compensation too high will
cause the circuit to oscillate wildly and change frequency, and may also
cause the electrode to behave in a similar manner. The extreme swings

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
3
in voltage may be harmful to neural tissue, and care should be exercised in using this
control. To a ccurate ly mea sure th e im pedanc e ve rif y a t t he OUTPUT connector that the
signal is a pure 1.0 kHz sine wave, and that the sine wave is at its maximum amplitude
(the point just before the signal becomes unstable).
NOTCH: This switch allows the Notch Filter to be included (IN) in the signal processing
path or bypassed (OUT). Warning: Although the Notch Filter provided can significantly
reduce unwanted interference from the power source, it will cause some distortion of the
signal, especially in frequencies below 100 Hz. Therefore, the Notch Filter should only
be used if other noise reduction techniques such as proper grounding and shielding are
inadequate.
LOW CUT-OFF: This rotary switch enables the user to select
the lower boundary frequency at which point the channel’s
input signal begins to be cut-off. Signals below the cut-off
frequency will be attenuated by a factor of 100 (-40 dB) per
decade decrease in the input signal frequency. For
example, if the LOW CUT-OFF switch is set at 100 HZ, then a 10
Hz signal will be attenuated by a factor of 100 while a 1 Hz
signal will be attenuated by a factor of 10,000. The Low Cut-
Off frequency should be selected based on the frequency content of the signal to be
recorded. One of the uses of this filter is to reduce slow variations or DC levels in the
input signal.
HIGH CUT-OFF: This rotary switch enables the user to select the upper boundary frequency
at which point the channel’s input signal begins to be cut-off. Signals above the cut-off
frequency will be attenuated by a factor of 100 (-40 dB) per decade increase in the input
signal frequency. For example, if the HIGH CUT-OFF switch is set at 1 KHZ, then a 10 kHz
signal will be attenuated by a factor of 100 while a 100 kHz signal will be attenuated by a
factor of 10 000. One of the uses of this filter is to reduce high-frequency noise that is
above the frequency content of the signal being recorded.
OUTPUT: This BNC connector provides the output signal from
the amplifier channel.
GND: This connector on the front panel provides access to
the circuit ground for its channel. Either the PROBE GND
connector or the front panel GND must be connected for
proper operation. Usually the PROBE GND connector is tied to
the indifferent lead. If you desire to have the current constrained to a known path you may
want to place the GND elsewhere. Actual GND placement depends on the application. For
low-noise recordings a ground connection should be made in the recording medium (i.e.
bath ground, animal ground, etc.).

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
4
Operating Instructions
Typical Set-Up Procedure
The Head Stage Probe is used to connect the extracellular electrodes to the amplifier. The
4 inch Connector Cables can be used to connect the Probe inputs to electrodes which
have standard gold male pin connectors. The GND connector on the front panel of the
amplifier should be used as the system ground in the particular recording medium (e.g.
bath or animal ground). Note: Either the Head Stage PROBE GND or the GND on the front
panel must be connected to provide a return current path. If neither ground is
connected the Head Stage Amplifier will saturate and no signal will be measured.
Care should be taken to keep the power cables from all instruments as far away as
possible from the recording set-up. Proper grounding and shielding techniques
should be used to insure a minimum of interference.
Recording
The MODE switch should be placed in the REC position. The LOW CUT-OFF Filter, HIGH CUT-
OFF Filter, and NOTCH Filter should be set according to the frequency content of the signal
to be recorded. The GAIN Switch should be set so that the signal at the OUTPUT connector
is less than ±10 V, otherwise higher and/or lower portions of the signal may appear cut-off
or flattened.
Stimulating
The MODE switch should be placed in the STIM position. Stimulation current (I) is
monitored by measuring the voltage (V) across an internal, fixed resistor (R = 1 k) in
series with the electrodes. Since I=V/R and R is known, the voltage is a measure of the
stimulus current. The internal resistor is in series with the indifferent lead (PROBE-) so that
excessive voltages do not appear at the Probe Amplifier inputs. Therefore, to insure that
the current in the indifferent lead is equal to and opposite of that in the active lead, only
isolated stimulus sources should be used. An added benefit of isolated stimulus sources
is that they produce less stimulus artifact than ground referenced sources. The Positive
Conductor of the Stimulus connector (Pin A; upper left; red wire in the stimulation cable) is
connected through the Probe to the active electrode lead, while the Negative Conductor
(Pin B; upper right; blue wire in the stimulation cable) is connected to the indifferent
electrode lead. The shield of the stimulation cable is not internally grounded in the
amplifier and needs to be grounded at the connection to the stimulator. When an isolated
stimulator is used the PROBE- connector must be grounded to function properly.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
5
Checking Electrode Impedance
At any time during an experiment the impedance of one or both electrodes can be
checked by selecting IMP with the MODE switch. In this mode, an internal oscillator
automatically passes a 0.1 µA, 1 kHz sine-wave current (I) through the electrode, and the
probe amplifier monitors the resultant voltage (V) that develops across the electrode.
Since R=V/I and I is known, the monitored voltage is a measure of the electrode
impedance.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
6
Theory of Operation
Overview
The Head Stage Probe, containing an high input inpedance, low-noise, differential
amplifier, is connected to the Model 1800 through a 9-pin Input connector assigned to
each channel. The Mode Switch for each channel controls the input configuration of the
Probe attached to that channel as well as the operation of the subsequent stages of the
amplifier. In Record Mode, a combination of the Probe and the main circuit amplify the
signal which appears across the two electrodes attached to the Probe. In Stimulus Mode,
the signal at the Stimulus connector to be applied to the electrodes and the Probe
monitors the stimulus current by measuring the voltage developed across a 1 kresistor
in series with the electrode. In Impedance Mode, an internally calibrated current is
passed through the Probe to one electrode, and the Probe monitors electrode impedance
by measuring the voltage that develops across the two electrodes.
The signal from the Probe passes through the differential amplifier which has a unity gain
in Record and Stimulus Modes and a gain of x0.01 in Impedance Mode. The signal then
passes through the Low Cut-Off Filter and is increased by a factor of 10. Next the signal
enters the Notch Filter if it is activated. Finally the signal passes through the High Cut-Off
Filter which has a unity gain in Stimulus and Impedance Modes and an adjustable gain
controlled by the Gain Switch while in Record Mode
Figure 2. Main circuit description and block diagram
*Only for impedance mode **Only for record mode
X 1 0
+
-X 1
X .01*
Mode
Rec.
Imp.
Stim.
X10 X1
x1
x10*
x100**
GAIN
Current
Source
Cap.
Comp.
He ad
S tage
Difference
AmplifierNotch
Filter
Low
Cut-OffHigh
Cut-Off
Output
IN
St
i
m
ul
u
s
OUT

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
7
Operational Modes
Record Mode
In Record Mode, the inputs of the Probe amplifier
A1 are switched by relay R1 (in the off position),
connecting them differentially across the two
electrodes in order to amplify with a x10 gain the
neural activity appearing at the electrode-tissue
interface. In this mode relay R2 is off so that the
Stimulus leads do not feed noise into the circuit.
The differential output signal of A1 passes through the differential amplifier A100 (unity
gain), the Low Frequency Cut-Off Filter A101 (x10 gain), and the Notch Filter A102 if
activated (unity gain), in that order. Finally the signal passes through the High Frequency
Cut-Off Filter A103, whose gain selection circuit is enabled by the gain relay RL14,
offering x1, x10, or x100 added gain.
Stimulus Mode
In Stimulus Mode, the differential inputs of the
Probe amplifier A1 are switched by R1 (in
the on position) so that they are across a 1
kresistor that is in series with PROBE-, the
indifferent electrode lead. At the same time,
relay R2 turns on and RL14 turns off. Relay
RL11 connects the stimulus source at the
STIMULUS connector to the electrode leads.
A stimulus current from an isolated source
passes through the PROBE+ lead to the active
electrode, returning through the PROBE- lead and the 1 kresistor. The current creates a
voltage across the resistor which is amplified by the Probe amplifier A1 and passes
through the differential amplifier A100, whose gain is now set to x0.01 by RL11. The signal
then passes through A101 (x10 gain), A102 if activated (unity gain), and finally through
A103, which has a unity gain set by RL14 through disabling the gain selection circuit.
Impedance Mode
In Impedance Mode, the differential inputs of
the Probe amplifier A1 are switched across
the two electrode leads by R1. At the same
time, relay R2 is on, RL14 is off, and RL11 is
switched such that the internal current source
is connected to the electrode leads. The
current source generates a 0.1 mA, 1 kHz
sine wave that passes through the
electrodes, and the voltage that develops is
Differential out
Probe+
Probe -
Head stage circuitry in Record Mode
1

Differential out
Probe+
Probe -
Stimulus +
Stimulus -
Differential out
Differential +
Differential -
0.1 uA p-p Sine Wave
Head stage circuitry in Stimulus Mode
Head stage circuitry in Impedance Mode

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
8
a measure of the electrode impedance. The output of A1 is then fed to A100, whose gain
is set at x0.01 by relay RL11. The signal next passes through A 101 (x10 gain), A102
(unity gain) and finally through A103, which has a unity gain set by RL14 through disabling
the gain selection circuit.
The current source consists of several parts. A stable timer (A300) produces a 15 V p-p
square wave at 1 kHz that is attenuated by a 5K potentiometer. The attenuated square-
wave is applied to a bandpass filter (A301) which passes the center frequency of the
square-wave but rejects the harmonics, resulting in a 1 kHz sine wave which is scaled to 2
V p-p by a 5K potentiometer. The 2 V p-p sine wave (TP300) is applied to an active
current source (A400 and A401), which converts the sine wave voltage to a sine wave
current of 0.1 µA p-p at 1 kHz. The calibrated current source is connected to relay RL11,
which switches the current to the electrode leads. The Capacity Compensation feedback
circuit (A402) reduces the amount of capacitance across the electrodes allowing only the
resistive component of the electrode to be measured.
Component Modules
Differential Amplifier
The Differential Amplifiers (A100, A200) make the transformation from a differential signal
to a single-ended signal. T102 and T202 are adjusted to balance this stage and
maximize the common-mode rejection.
Low Frequency Cut-Off Filter
The Low Frequency Cut-Off Filters (A101, A201) are second-order Butterworth high-pass
filters with selectable cut-off points.
Notch Filter
The Notch Filters (A102, A202) are tuned to the line frequency. The circuit consists of a
twin-T network in a feedback loop with an operational amplifier.
High Frequency Cut-Off Filter
The High Frequency Cut-Off Filters (A103, A203) are second-order Butterworth low-pass
filters with selectable cut-off points.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
9
Problem Solving
If you are experiencing problems with the Model 1800, the following procedure will assist
in diagnosing the source of the problem. It is important to follow these steps in the order
presented and change only those controls listed. For the following procedures, a variable
frequency function generator capable of producing sine wave outputs and an oscilloscope
will be needed. A simple resistor voltage divider may be needed to obtain the small
signals in the mV range which should be applied to the probe amplifier inputs in order to
test the system. Make sure that all input cables are shielded. The following procedures
assume that the Model 1800 has been properly adjusted, and calibrated.
Initial Settings
Controls Inputs / Observations Adjust / Check
LOW CUT-OFF: 10 HZ
HIGH CUT-OFF: 10 KHZ
Record Mode
Controls Inputs / Observations Adjust / Check
MODE: REC Apply a 1 mV p-p, 500 Hz sine Check for 100 mV p-p,
GAIN: X100 wave signal to the PROBE INPUTS 500 Hz undistorted signal
Observe voltage at OUTPUT with
an oscilloscope
GAIN: X1000 Check for 1 V p-p, 500 Hz
undistorted signal
GAIN: X10 000 Check for 10 V p-p, 500 Hz
undistorted signal
Stimulus and Impedance Modes
Controls Inputs / Observations Adjust / Check
MODE: STIM Connect a 1 Mresistor (± 5%) Check for 100 mV steps in
across PROBE+ and PROBE- sync with the input pulses
Connect PROBE- to GND
Apply 1 µA pulse to STIMULUS
from an isolated current source
Observe voltage at OUTPUT
MODE: IMP Disconnect 1µA pulse to STIMULUS Check for 100 mV p-p,
CAPACITY COMP.: adjust 1 kHz sine wave

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
10
Noise and Output Level
Controls Inputs / Observations Adjust / Check
MODE: REC Connect PROBE+ and PROBE- Check for 0.0V±25 mV p-p
LOW CUT-OFF: 10 HZ to PROBE GND or less
HIGH CUT-OFF: 10 KHZ Observe voltage at OUTPUT
GAIN: X1000
Low Frequency Cut-Off Filter
Controls Inputs / Observations Adjust / Check
LOW CUT-OFF: see note Apply 1 mV p-p sine wave to Check for voltage as
PROBE+ and PROBE- indicated in note
Observe voltage at OUTPUT
Note: Repeat this test for each LOW CUT-OFF setting. Each time, select an
input signal frequency below the LOW CUT-OFF setting to begin, then increase it
to at least ten times above the LOW CUT-OFF setting. When the input signal
frequency is between the LOW CUT-OFF setting and the HIGH CUT-OFF setting the
signal at OUTPUT should be 1 V. In contrast, when the signal frequency is
decreased below the LOW CUT-OFF setting, the signal at OUTPUT will approach 0
V. As the inp ut s ignal f r equen c y is i ncreased ab ove the HIGH CUT-OFF setting, the
signal at OUTPUT will also approach 0 V.
High Frequency Cut-Off Filter
Controls Inputs / Observations Adjust / Check
LOW CUT-OFF: 10 HZ Apply 1 mV p-p sine wave to Check for voltage as
HIGH CUT-OFF: see note PROBE+ and PROBE- indicated in note
Observe voltage at OUTPUT
Note: Repeat this test for each HIGH CUT-OFF setting. Each time, select an
input signal frequency above the HIGH CUT-OFF setting to begin, then decrease it
to at least ten times below the HIGH CUT-OFF setting. When the input signal
frequency is between the LOW CUT-OFF setting and the HIGH CUT-OFF setting the
signal at OUTPUT should be 1 V. In contrast, when the signal frequency is
increased above the HIGH CUT-OFF setting, the signal at OUTPUT will approach 0
V. As the inp ut s ignal f r equen c y is dec r eased be low the LOW CUT-OFF setting,
the signal at OUTPUT will also approach 0 V.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
11
Notch Filter
Controls Inputs / Observations Adjust / Check
LOW CUT-OFF: 1 HZ Apply 1 mV p-p sine wave to Check for voltage as
HIGH CUT-OFF: 1 KHZ PROBE+ and PROBE- indicated in note
NOTCH: see note Observe voltage at OUTPUT
Note: Repeat this test for each NOTCH setting. Each time, begin with the input
signal at 10 Hz and then increase it to 100 Hz. With NOTCH: OUT, the signal at
OUTPUT should remain 1 V. With NOTCH: IN, the signal at OUTPUT should be
substantially reduced around 60 Hz (or 50 Hz if your instrument has been
factory preset for a 50 Hz environment) and less so above and below this
frequency.
.01 Hz 1 Hz 10 Hz 100 Hz 1 kHz 10 kH z 100 kHz
30 dB
40 dB
10 dB
20 dB
0 dB
Low Cut-Off High Cut-Off
Notch
Frequency in Log Scale
dB = 20 log X V = X * V
Ad d 2 0 d B t o v e rt i ca l s ca l e f o r GA I N o f X 1 00 0 ,
a nd 4 0 d B f o r G AI N o f X 1 0K

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
12
Calibration Proceedures
The calibration interval is the lesser of 1000 hours of operation or 6 months. Somewhat
greater drift can be expected in the first 100 hours of operation as the semiconductors
age. Adjustments should only be made after the instrument is fully warmed up (at least 15
minutes).
Adjustment, integrated circuit, and test point locations are shown in the following figure.
NOTE: It is important to complete this entire procedure in sequence. If any adjustment is
made, all of the following adjustments must be made in order to ensure that the
specifications will be met.
CAUTION: Do not open the HeadStage probe for any of these proceedures.
T101
R L 1 5
A 4 0 0
A 4 0 1
A 40 2
T P 4 00 T3 0 0
A3 0 0
T P 30 0
A3 01
A 502
A 5 0 0
A 5 0 1
RL 2 5
TP 500
TP 1 0 0
A 1 0 0
A 1 0 1 TP 1 0 0
T 1 00
RL 11 RL 1 2 R L13
C R1 0 0
C R10 0
A102
T P 10 2
A 1 0 3
T1 03
TP 10 3
TP 10 4
CR 20 0
CR 2 0 1
R L 2 1 RL 2 2
T 2 01
R1 23
T P2 0 2
A2 0 2
R1 24
A20 3
T20 3
TP2 03
TP 20 4
TP2 00
A2 00
T 2 00
A2 01 TP 201
T2 0 4
T2 05
T 1 0 4
T 1 0 5
T3 01
T1 0 2 T 202
RL1 4

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
13
Initial Settings
Controls Inputs / Observations Adjust / Check
POWER: OFF Connect HeadStage Probes
LOW CUT-OFF: 1 HZ
HIGH CUT-OFF: 20 KHZ Tie PROBE GND to PROBE+
CAPACITY COMP: and PROBE-
fully counter-clockwise
MODE: REC
GAIN: X10K
NOTCH: OUT
POWER: ON
Power Supply
NOTE: Measure the following voltages with an oscilloscope. A voltage is
considered to be incorrect if it displays excessive noise visible in a 20 mV or
greater ripple. Operational amplifiers are static sensitive devices. Please
properly ground yourself and your workstation before removing any components.
Follow PROCEDURE Abelow for each operational-amplifier listed:
Channel 1: A100, A101, A102, A103, A400, A401, A402
HeadStage: A1 (Test at locations CR100: +15 V and CR101: -15 V)
Channel 2: A200, A201, A202, A203, A500, A501, A502
HeadStage: A1 (Test at locations CR200: +15 V and CR201: -15 V)
Common: A300 (pins 4 and 8: +15 V, do not test pin 7),
A301 (pin 4: -15 V and pin 7: +15 V)
If a voltage is found to be incorrect, please follow PROCEDURE B. If the voltage is incorrect in
Procedure A, but correct in Procedure B at the socket, then this indicates a problem with the
op-amp: please contact the factory for a replacement part. An incorrect voltage at the socket
in Procedure B indicates a problem with the power supply: the instrument must be returned to
the factory for repair.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
14
PROCEDURE A:
Controls Inputs / Observations Adjust / Check
Observe voltage on pin 4 Check for -15 V
of the op-amp
Observe voltage on pin 7 Check for +15 V
of the op-amp
PROCEEDURE B:
Controls Inputs / Observations Adjust / Check
POWER: OFF
Remove op-amp
POWER: ON
Observe voltage on pin 4 Check for -15 V
of the op-amp socket
Observe voltage on pin 7 Check for +15 V
of the op-amp socket
POWER: OFF
Replace op-amp or
remove an additional
op-amp for further testing
POWER: ON
Zeroing
The following procedure calibrates Channel 1.
Controls Inputs / Observations Adjust / Check
POWER: ON Connect PROBE+ and PROBE- Adjust T100 for 0.0 V
to instrument GND
Observe voltage at TP101
Observe voltage at TP102 Adjust T101 for 0.0 V
Observe voltage at TP103 Adjust T103 for 0.0 V
Repeat this proceedure for locations TP201 through TP203 and T200 through
T203 to calibrate Channel 2.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
15
Test Points
Note: The following test points should be checked sequentially from the input
side of the amplifier to the output side. If a particular test point voltage is
incorrect, then it is likely that the amplifier or circuitry immediately preceding
the test point is malfunctioning. All readings are peak-to-peak and the
waveforms should be undistorted sine waves.
The following proceedure calibrates Channel 1.
Controls Inputs / Observations Adjust / Check
MODE: REC Apply a 1 mV p-p, 1 kHz signal
HIGH CUT-OFF: 10 KHZ between PROBE+ and PROBE-
LOW CUT-OFF: 100 HZ
Observe voltage at RL11 pin 8 Check for 5 mV p-p at
and RL11 pin 9 both pins and 180 degree
phase shift between pins
Observe voltage at TP100 Check for 10 mV p-p
Observe voltage at TP101 Check for 100 mV p-p
NOTCH: IN Observe voltage at TP102 Check for 100 mV p-p
NOTCH: OUT Observe voltage at TP102 Check for 100 mV p-p
GAIN: X100 Observe voltage at OUTPUT Check for 100 mV p-p
GAIN: X1000 Observe voltage at OUTPUT Check for 1 V p-p
GAIN: X10K Observe volgate at OUTPUT Check for 10 V p-p
Repeat this proceedure for locations RL22 and TP200 through TP202 to
calibrate Channel 2.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
16
Common-Mode Rejection
The following proceedure calibrates Channel 1.
Controls Inputs / Observations Adjust / Check
LOW CUT-OFF: 1 HZ Tie PROBE+ to PROBE- and
HIGH CUT-OFF: 1 KHZ apply a 1 V, 100 Hz signal to both
Observe the voltage at TP100 Adjust T102 for a minimum
with an oscilloscope voltage (typically only a few
mV), however this voltage
should not be a “clean”,
undistorted sine wave due
to the balanced gains of the
differential amplifier
Repeat this proceedure for locations TP200 and T201 to calibrate Channel 2.
Impedance
Current Injection
Controls Inputs / Observations Adjust / Check
Observe TP300 with an Adjust T300 for a maximum
oscilloscope p-p output
Check that the output
signal is 1 kHz
Observe voltage at OUTPUT Adjust T301 for 2 V p-p
Operation Test
Controls Inputs / Observations Adjust / Check
MODE: INP Connect a 10 Mresistor between
PROBE+ and PROBE-
Observe voltage at OUTPUT Adjust CAPACITY COMP.
clockwise until just before
the signal oscilates
Check that the voltage is
1 V p-p at 1 kHz
Repeat this proceedure to calibrate Channel 2.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Te l o p h o ne : 8 0 0 - 42 6 - 1 3 0 6 * 3 6 0 - 68 3 - 8 3 0 0 * FA X : 3 6 0 - 6 8 3- 3 5 2 5
E-mail: [e-mail] * Website: http://www.a-msystems.com
17
Specifications
Record Mode
Gain settings available (x100, x1000 or x10 000) ± 5%
Noise 3 µV rms (10Hz to 10kHz)
Stimulus Mode
Output current ratio 0.1 V/ 1 µA
Maximum output current reading ± 10 V or ± 100 µA
Maximum stimulus current 10 mA
Maximum stimulus voltage
Pin A (+ diff) upper left pin hole ± 100V
Pin B (-diff) upper right pin hole ± 15V
Impedance Input
Output impedance ratio 1 M/ 0.1 V
Maximum output impedance reading 4 V or 40 M
General Electrical
Input impedance 100 000 M, typical
Output Impedance < 1 
Common mode rejection Adjustable to better than -80 dB
Notch Filter Better than -30 dB at 60 Hz;
Better than -25 dB at 50 Hz
Input bias current 200 pA, typical
DC Compliance range At least ± 1 V DC
Output dynamic range ± 10 V AC, minimum
Low cut-off frequency settings 0.1 Hz, 1 Hz, 10 Hz, 100 Hz, 300 Hz ± 15%
Low cut-off filter gain -40 dB / decade
High cut-off frequency settings 500 Hz, 1 kHz, 5 kHz, 10 kHz, 20 kHz, ±15%
High cut-off filter gain -40 dB / decade
Power 115 V, 60 Hz or 230 V, 50 Hz; < 5 W total
Physical Dimensions
Width 17 inches (43.2 cm)
Height 4.75 inches (12.1 cm)