A-MSystems 1900 User manual

INSTRUCTION MANUAL
FOR
POLAROGRAPHIC AMPLIFIER
MODEL 1900
Serial #__________
Date____________
A-M Systems
PO Box 850
Carlsborg, WA 98324
U.S.A.
360-683-8300 ♦800-426-1306 FAX:
360-683-3525
http://www.a-msystems.com
Version 9.0
March 2020

Contents
General Description........................................................................................................................................1
Instrument Features .............................................................................................................................................1
Controls and Connectors......................................................................................................................................2
Operating Instructions...................................................................................................................................4
Polarographic electrodes......................................................................................................................................4
Instrument Set-Up and Calibration......................................................................................................................6
Problem Solving ..................................................................................................................................................9
Theory Of Operation....................................................................................................................................11
Specifications..................................................................................................................................................13
Warranty and Service..................................................................................................................................17
Each Polarographic Amplifier is delivered complete with:
Rack Mount Hardware
NOTE
This instrument is not intended for clinical measurements using human
subjects. A-M Systems does not assume responsibility for injury or
damage due to the misuse of this instrument.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
1
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
General Description
Instrument Features
The Polarographic Amplifier Model 1900 is designed primarily for use with
microelectrodes (such as oxygen and hydrogen electrodes) which produce a current
response to an applied polarization voltage in the presence of the sensed gas. The
Model 1900 converts the input current to an output voltage, scaled and offset by user
operated controls. The voltage is output for subsequent analysis by the researcher.
The polarization voltage applied to the electrode may be set internally via manual
controls or through an external signal source. In either case, the polarization may be
turned off by a separate gate signal without disturbing other settings.
No head stage is required to achieve very low bias current (<1 pA, nominal, before
adjustment) using an actively-driven shielded sensor cable. Standard BNC connectors
are used for all signal connections. The sensor input connector can be operated with a
driven shield to minimize cable and connector leakage currents for applications
requiring the highest sensitivity; or with a grounded shield for greater convenience in
less demanding applications. The reference input may be set to differential or ground.
In differential mode, negligible current flows through the reference electrode,
eliminating reference electrode IR (voltage drop) errors. In ground mode, the
requirement for a separate ground electrode is eliminated.
The output scaling can be selected to read out in absolute current measured in nA, or
in mmHg, expanded 10x mmHg, percentage, or kPa. The input “zero” current may
be set up to one fourth of the full scale current range. In this way, any constant
leakage current (especially that from electrode current which flows in the absence of
any reagent gas) may be readily ignored. The gain is adjustable with step and fine
controls. Adjustment of the gain does not require readjustment of the zero current.
System sensitivity is high, with a maximum resolution of 0.1pA when in 100 pA scale.
The output can be read directly using an internal digital meter (3 1/2 digits), and can be
connected to chart recorders, FM tape recorders, or computers. The digital meter can
also be used to measure the polarization voltage.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
2
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Controls and Connectors
The Model 1900 has been designed to ease polarographic measurements, while
accommodating the imperfections of real electrodes. This section gives a brief
description of the controls and connectors.
INPUT
The INPUT section is directly associated with the electrodes.
The sensing electrode is connected to the SENSOR input.
The reference electrode is connected to the REF input.
While the shield of the REF input connector is permanently
attached to ground, the shield of the SENSOR input may be
grounded (GND) via the SHIELD switch or may be actively
driven (ACTIVE), in order to reduce leakage currents in the
interconnecting hardware. The REF input itself may be
connected to ground (GND) via the REF switch, or the
amplifier may be operated differentially (DIFF).
POLARIZATION
The POLARIZATION section controls are used to bias the
sensing electrode at the required potential relative to the
reference, whether the reference is at ground or operating
differentially. The polarization voltage source can be set to
EXTernal INTERNAL+, or INTERNAL -, with a rotary switch. An
external polarization voltage source is connected to the EXT
IN connector. Alternatively, an INTERNAL polarization
voltage level is set with the INTERNAL VOLTAGE control.
Whatever the source, the polarization voltage may be
turned on or off using a gate signal applied to the GATE IN
connector. The applied polarization voltage may also be
monitored externally at the MONITOR OUT connector.
SCALING
The SCALING section provides control over the gain and
offset settings. Offset is controlled by the FINE ZERO control,
which may be switched ON or OFF with the ZERO CURRENT
switch. The gain is controlled in steps by the NANOAMPERS
rotary switch, and continuously over a narrower range by
the FINE GAIN control.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
3
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
OUTPUT
The form of the output is controlled by the OUTPUT selector switch. In
the CURRENT mode, the measurements are absolute (not sign
adjusted). An additional x10 gain (expansion gain) is inserted in the
mmHg x10 and % x10 modes for increased resolution with small
currents. The decimal point of the panel meter is shifted, maintaining
the original sense of the measurement, while providing the higher
resolution. The output voltage is available externally via the BNC
connector for continuous recording with a chart recorder, or
computerized data acquisition equipment.
METER
The METER may be used to monitor either the
POLARIZATION voltage (unaffected by the GATE IN signal), or
the OUTPUT voltage. pA and nA indicators supplement the
decimal point location on the METER to provide a 5-decade
sensitivity range without loss of resolution.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
4
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Operating Instructions
The Model 1900 has been designed to be simple and intuitive to operate, while allowing a
high degree of flexibility and performance. A brief description of pertinent polarographic
electrode characteristics is included in this section along with operating instructions for the
instrument and solutions to common problems which are encountered in its use, in order
to assist with the effective use of this instrument.
Polarographic electrodes
The most important property of polarographic electrodes is that their current, instead of
their voltage, varies with a change in the concentration of the sensed substance (most
commonly a dissolved gas such as oxygen)1.
Figure 1. Typical oxygen electrode response
To use such an electrode, a bias voltage is applied which intersects the plateau
region(s), allowing the current response to be linear over a physiologically meaningful
range. The current amplitude is often extremely small, typically in the nano- or
picoampere range. These characteristics require that an amplifier with current-to-voltage
capabilities be used in order to measure the concentration of the sensed substance.
1. An excellent description of the theory, construction, and application of polarographic electrodes can be found in: Irving
Fatt, Polarographic Oxygen Sensor, Malebar FL: Robert E. Kreiger Publishing Co., 1982.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
5
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
The polarographic electrode can be used as part of a 2 electrode or a 3 electrode
configuration (see Figure 2 and Figure 3):
The 2 electrode configuration is simple and convenient. The polarization voltage is
impressed across the two electrodes. Notice, however, that the sensed current must flow
through the reference electrode. The reference electrode may have an impedance of many
MV. In such a case, the IR drop within the reference electrode may be sufficient to bias the
polarographic electrode out of the plateau region of the electrode. This problem can be
eliminated with the addition of another electrode.
Figure 2. Two-electrode configuration Figure 3. Three-electrode configuration
Using the 3 electrode configuration, the polarographic current now flows through the
separate ground return electrode. The placement of the ground return electrode can be
almost anywhere, as long as it is in electrical contact with the tissue.2The reference
electrode must be close to the tissue being sensed in order that the tissue voltage being
sensed by it be accurate. The current sensed is always that which is flowing in the
SENSOR lead. This allows flexibility in grounding arrangements.
For either the 2 or 3 electrode configuration, the voltage impressed on the polarographic
electrode is the sum of the reference voltage and the polarization voltage. For the 2
electrode configuration, this means that the polarization voltage is relative to ground, which
may be offset from the tissue potential by the IR drop in the ground/reference electrode.
For the 3 electrode configuration, the polarization voltage is relative to the reference
electrode voltage.
2. Some additional consideration may be necessary if the “ground” currents are allowed to be coupled through neural
tissues. Unwanted complications may result if these currents stimulate responses. The same considerations apply for
the 2 electrode configuration. The amount of current flowing through most polarographic electrodes is low enough that
this should not be a problem for nearly all researchers.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
6
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Instrument Set-Up and Calibration
Note: In most cases, the settings of the Model 1900 will not have to be changed from experiment to
experiment, except for calibrating the electrodes.
Connecting the Electrodes to the Input
The characteristics of polarographic electrodes make it necessary to exercise extreme
care in connecting the Model 1900 with the electrode set. The degree of difficulty
involved depends upon the quality of the electrode, and the magnitude of the response
relative to leakage currents and other sources of noise.
The polarographic electrode is connected directly to the SENSOR input. Many
commercially available polarographic electrodes have BNC connectors, and may be
used directly. Set the SHIELD and REF switches to the GND position for these
electrodes. For electrodes with low responses in the pA range, particularly when
maximal resolution is required, it may be necessary to drive the sensor cable shield,
with the SHIELD switch in the ACTIVE position. This reduces possible leakage
currents in the cabling by “bootstrapping” the cable shield to be at the same potential
as the inner conductor. This is especially important if the polarization voltage is to be
varied without readjusting the zero current. However, care must be taken to ensure
that the shield is not otherwise connected to ground (or any other potentials) for the
driven shield to work correctly. If this is not possible (or not necessary), theSHIELD
switch must be set to GND.
The reference electrode is connected directly to the REF connector. Some electrodes
incorporate a reference connection through the shield of the sensing electrode. In this
case, set the REF switch to GND; no other reference is required. For the 3 electrode
configuration, set the REF switch to DIFF. The return current path can be made either
through the outer shield of the REF connector, or via the front panel GND connector.
Some situations (particularly where space prohibits adding another electrode) require
that all shields be connected together, and to ground. The REF switch should be set to
GND in this case.
Controlling the Polarization Voltage
Polarographic electrodes need a bias voltage to ensure that they operate within their
respective plateau regions. The Model 1900 provides several options for solving this
problem. For most situations, the POLARIZATION selector switch is used. Set the
polarity to INTERNAL+ or INTERNAL-, and adjust the voltage using the INTERNAL
VOLTAGE control. The EXT IN signal is effectively disconnected in this mode. The
polarization voltage can be observed on the panel METER by setting the METER switch
to the POLARIZATION position. The readout is in mV. Oxygen electrodes are usually
set at -600 mV, and hydrogen electrodes at +250mV. The polarization voltage may
also be monitored via the MONITOR OUT connector.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
7
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
For some situations, it may be desirable to set the polarization voltage from an external
source, such as a computer controlled D/A converter. Simply set the POLARIZATION
selector switch to EXTERNAL, and connect the source to the EXT IN connector. The
INTERNAL voltage is disconnected in this mode. The polarization voltage may be
monitored at the METER or at the MONITOR OUT connector.
Leaving the GATE IN connector disconnected is sufficient to guarantee that the specified
polarization voltage appears at the polarographic electrode. If the GATE IN is driven low
(e.g. by shorting the input to ground, or with a low TTL signal), the polarization voltage
is turned off, and the voltage at the polarographic electrode is set to the same potential
as the reference electrode. The polarization voltage available at MONITOR OUT reflects
the state of the signal at GATE IN. However the METER,when set to POLARIZATION
mode, always displays the polarization voltage regardless of the state of the signal at
GATE IN so that the voltage can be set more easily without disturbing the electrode.
The OUTPUT will continue to indicate the current flowing in the sensor electrode.
Setting the Output Mode
The type of output signal desired should be selected before beginning to calibrate the
electrodes. You may switch between expanded and unexpanded modes (% and % x10;
or mmHg and mmHg x10) without any complication, but switching between output types
requires recalibration. This is necessary because no two electrodes are identical.
Therefore, in general there is no interconvertibility of signal types, such as CURRENT
and mmHg, except in the context of a specific electrode. However, switching between
expanded and unexpanded modes, increasing gain when the signal dwindles, or
decreasing gain to keep the signal within range may be done atany time. The % and %
x10 output modes may be used for scaling the output in kPa.
Calibrating the Electrode
If electrode current is of interest, no electrode calibration is necessary. Simply set the
ZERO CURRENT to OFF, turn the FINE GAIN fully clockwise, and set the NANOAMPERES
scale to the desired range. The Model 1900 is calibrated and ready.
If the signal is to be displayed in mmHg or %, the electrode must be calibrated, since
there are no “standard” electrodes. The Model 1900 has been designed to ease some
of the difficulty involved in calibrating electrodes. The following calibration procedure
example uses the case of measuring oxygen dissolved in an aqueous environment.
While a specific application may be different, the calibration procedure will likely be
analogous.
In addition to the electrode set, cables, and the Model 1900, a method must exist to
control the concentration of the substance being measured. The test solution should
mimic the features of the tissue to be tested later. Important features to mimic may
include both chemical and physical properties of the solution, such as temperature and
osmolarity. Which features are important depends on the specificity of your electrode;
that is, the degree to which the electrode is sensitive to factors other than those being

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
8
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
measured in the experiment. Consult the electrode manufacturer for further
information regarding the sensitivity of the electrode any additional factors. A set of
control experiments is advisable to safeguard against unforeseen interactions, and
must be created with regard to the specific experiments to be conducted.
Sample Electrode Calibration Procedure
The first step is to calibrate the zero point. Set the NANOAMPERES switch to the desired
range. It may be necessary to expose the electrode to a test solution with the
maximum expected concentration first, in order to determine the maximal current.
Connect the electrode set (2 electrode or 3 electrode) to the Model 1900 as described
above. The test solution should have as low a concentration of the substance as
possible. It is highly desirable to achieve zero concentration, so that no interactive
readjustment will be needed after setting the FINE GAIN later in this procedure. For the
specific case of oxygen measurements, a warmed physiological saline solution can be
depleted of oxygen by bubbling pure nitrogen gas through it. Ensure that the ZERO
CURRENT switch is ON, and adjust the FINE ZERO control for a zero reading, either at the
OUTPUT connector, or at the METER set to OUTPUT.
The second step is to calibrate the gain. Move the electrodes into a new solution (or
change the concentration in the current solution) to have a known concentration. The
selected concentration should be at or slightly greater than the maximum concentration
which is expected in the experiment. Set the FINE GAIN control such that the reading is
correct when observed at either the METER or the OUTPUT connector.
If it was possible to establish a true zero concentration, the electrodes are now
stabilized. If the NANOAMPERS switch was not changed, the calibration is complete.
Otherwise, this process should be repeated until no further adjustment is required.
The degree of interaction is reduced as the low concentration solution approaches a
zero concentration.
Display Meter and Output
The METER consists of a 3 1/2 digit display. The scale indication takes two forms:
decimal point movement and LED range indication. These are driven from the
condition of the OUTPUT selector switch and the NANOAMPERES selector switch. The
display meter has an additional one-pole lowpass filter (bandwidth about 0.9 Hz),
which does not influence the frequency response of the rest of the instrument.
The sign of the METER display (and the signal at the OUTPUT connector) is positive for
(conventional) current flowing out of the input connector while the OUTPUT selector
switch is set to CURRENT. Once the electrode set has been calibrated the
measurements are available directly from the readout without further scaling. Voltages
are scaled (within a decimal-point movement) and are simultaneously available at the
OUTPUT connector)

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
9
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Problem Solving
Most of the difficulties in making polarographic measurements are associated with
imperfect electrodes. Ideally, the electrode will have a wide, perfectly horizontal
plateau region, so that small variations in the polarization voltage will have no effect on
the resultant current. In practice, this rarely occurs. The plateau region is generally
tilted, and a plateau at one concentration may occur at a different polarization voltage
than a plateau at a much different concentration. The polarization voltage should be
chosen to pass through the flattest part of the plateau regions of interest.
Another problem associated with polarographic electrodes is the change in electrode
characteristics with time and temperature. Temperature problems are minimized by
maintaining a constant temperature while calibrating and taking the desired
measurements. In most physiologically-related research, the application temperature
is nearly constant. Applications in which temperature does vary significantly may
require greater electrode characterization so that the desired measurements may be
corrected for temperature effects after the experiment.
Electrode drift with time mostly occurs as a result of tissue penetration, but may also
occur due to contamination by chemicals within the tissue being studied.
Polarographic electrodes are often delicate; since less damage usually occurs on
leaving the tissue than on penetration, it may be necessary to calibrate the electrodes
after the experiment. The recorded results must then be modified appropriately.
Electrode surface contamination by chemicals, especially tissue proteins, can occur
which alter the redox potential of the electrode. This effect may be reduced by
turning off the polarization voltage between measurements using a signal applied at
the GATE IN connector to extinguish electrode current flow between measurements.
Solution movement over the sensor surface can change apparent electrode sensitivity
(“stir artifact”). A greater degree of movement and a larger catalytic surface will
produce a larger “stir artifact” effect. Membranes over the sensing surface greatly
reduce this effect. The “Clark” oxygen electrode is a classic implementation of this
approach.
To test the basic functionality of the Model 1900, replace the electrode with a 10 MV
resistor. Set REF and SENSOR switches to the GND position. Use the METER to set an
internal polarization voltage of +1.000 V as follows: set the POLARIZATION switch to
INTERNAL+, disconnect any signals from the GATE IN and EXT IN connectors, set the
ZERO CURRENT to OFF, switch the METER to CURRENT. The METER should read +100
nA (within the tolerance of the resistor and instrument). Switching the POLARIZATION
to INTERNAL- should give reading of -100 nA. Finally, switching the POLARIZATION to
EXT (with no signal applied at the EXT IN connected) or shorting the GATE IN connector
should result in 0.0 nA.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
10
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
The following chart includes a brief summary of typical problems encountered while
using the Model 1900, along with the most common causes and solutions.
If the Model 1900 appears to be malfunctioning, contact A-M Systems, Inc., or the
dealer from which the instrument was purchased. Contact information for A-M
Systems, Inc. is listed on the cover page of this manual. Further information may also
be found in the section “Warranty and Service” in this manual.
Problem Cause/Solution
METER is dark • Blown fuse: replace fuse on back panel
• Improper power connection
METER constantly blinks • SENSOR input wire is shorted
(always overdriven) • REF not connected properly
• GND connection missing while using DIFF
(3 electrode) method
METER reading does not change as • METER switch not set to POLARIZATION
INTERNAL VOLTAGE control is rotated • POLARIZATION source switch set to EXT
• GATE IN is shorted or otherwise held “low”
• Nonfunctional or damaged electrode
METER does not respond to • METER switch set to POLARIZATION
concentration changes • GATE IN is shorted or otherwise held “low”
• POLARIZATION source is EXT but no input
signal is applied
• Open circuit in SENSOR connection
• Nonfunctional or damaged electrode
Negative METER reading • Excessive ZERO CURRENT compensation
• Negative POLARIZATION voltage in
CURRENT mode

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
11
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Theory Of Operation
The operation of the Model 1900 is summarized in the block diagram below (Figure 4).
The most critical portion of the instrument is the Current to Voltage transducer (U100,
U101, U102, U500A). This section accepts the polarization voltage, adds the reference
voltage, and applies it to the input. At the same time, it detects the current flowing through
the input port. It converts this current into a ground-referenced voltage which is passed to
succeeding stages.
Figure 4. Instrument block diagram
The Polarization Generator generates and conditions a voltage suitable for the
Current-to-Voltage Transducer. Internal polarity and amplitude are controlled, or an
external polarization source is selected at this point. This signal is passed to the Meter
and to the Gate.A buffered, gated polarization voltage is passed to the Current-to-
Voltage Transducer and to the monitor output.
The low pass filter (approx. 15Hz, 2-pole transitional Butterworth-Thompson filter)
subtracts the zero current signal from the output of the Current-to-Voltage
Transducer, providing a method for eliminating the zero-concentration leakage
current (and any other steady state leakage current as well). The sign of the zeroing
current is automatically switched to oppose the input current flow, based on the sign
of the polarization voltage. Gain is set at the output of the Low Pass Filter with a
potentiometer. A high input impedance notch filter receives the output of the Gain

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
12
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
potentiometer, filters out line-frequency noise, and passes the result to an output
buffer.
The output buffer is used to scale the signal, depending on the state of the output
switch. For mmHg and % modes, the sign of the gain through this section is
dependent on the sign of the polarization voltage in order to ensure that the output is
always positive (although it is possible to force the output and meter negative for small
input currents with large zero current signals).
Not included in the block diagram are the circuits controlling the LED and decimal
point logic. The LED and decimal points are controlled based on the nanoamperes
and output selector switch settings. The decimal points are suppressed when the
meter is set to read the polarization voltage; the readout is then in mV.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
13
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Specifications
Input Section
Sensor Input
Offset current with < ± 1.0 pA at 25°C ambient temperature
ZERO CURRENT: OFF, < ± 4.0 pA at 40°C ambient temperature
SHIELD: ACTIVE
Note: The input leakage is an internal value. It adds to the current flowing through any attached
electrode. Additional leakages from exterior sources, including cables, may occur.
Input impedance < 50 Ω
+ 2 µV / (scale current)
Maximum continuous applied
voltage (without breakdown)
Sensor Shield
± 12 V
Shield driver output impedance 5.2 kΩ± 5%
Shield driver output current > ± 1 mA
Maximum continuous applied
voltage (without breakdown)
Reference Input
± 12 V
Input leakage current < 300 pA at 25°C ambient temperature;
40 pA, typical
Input impedance with
REF: DIFF
1011 Ω, typical
Input impedance with
REF: GND
< 2.0 Ω
Voltage compliance range
(offset between reference, gnd)
At least ± 2.5 V, referred to ground
Maximum continuous applied
voltage (without breakdown) ± 12 V

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
14
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Polarization Section
Internal Voltage
Range < 0.10 V to > 1.0 V
Settability Within 1 mV of any value within the range
Accuracy Within ± (1% + 2 mV) of the potential
indicated on the Meter
Drift < (0.02% of setting/hour + 100 µV/°C)
External Input
after warmup period
Maximum linear range ± 1.5 V
Input resistance 1 MΩ± 1%
Accuracy Within ± (0.2% + 2 mV) of the potential
indicated on the METER;
Within ± (1% + 12 mV) of the potential
Gate Input
applied at the connector
Gate ON condition 2.4 to 15.0 V (or open-circuit)
Gate OFF condtion -5.0 to 0.8 V (or short-circuit)
Input current Less than 50µA is required to establish the
OFF condition. More current may flow
for gate control voltages above +5 V or
below -2 V
Applied polarization voltage Within ± 1.0 mV of the reference potential
Monitor Output
with Gate OFF
Output impedance 1 kΩ± 2%
Accuracy Within ± (2% + 15 mV)

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
15
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Scaling
Step Gain Accuracy
The accuracy specifications are guaranteed only when the SHIELD switch set to ACTIVE, and do not
include external error sources such as electrode non-linearity. The FINE GAIN control should be fully
clockwise.
Full Scale Current
Accuracy 3
± (% full scale + equivalent offset)
1000 nA 1% + 1.2 nA
100 nA 1% + 0.15 nA
10 nA 2% + 40 pA
1 nA
0.1 nA 3% + 8.0 pA
5% + 2.0 pA
Linearity (no expansion) Within ± (0.1% of reading + 0.1%
of full scale)
Linearity (with x10 expansion) Within ± (0.25% of reading + 0.2%
Fine Zero
of full scale)
Range < 0.01x to > 0.25x the full-scale setting
Settability Within 0.1% of the full-scale setting. This
equals 0.1 pA in the 100 pA setting.
Fine Gain
The full clockwise position is ‘calibrated’ to the value on the step scaling control. Counter-clockwise
rotation of this control reduces the output gain sensitivity.
Range < 0.1x to 1.00x the full-scale setting
Settability Within 0.2% of the full-scale setting
3. This applies at 25°C ambient temperature. Somewhat greater offsets may occur at higher temperatures. See
the INPUT section for more details.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
16
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Output
Digital Panel Meter
Accuracy (OUTPUT mode) Within (0.1% of the range + 2 counts)
of the output
Settling time (OUTPUT mode) < 1.0 sec to settle within 1.0%;
< 6 sec for the least significant digit to
Total Drift and Noise
settle after a 100% scale
Initial offset ± 2 mV (± 5 mV for expanded scales)
Drift due to temperature < 0.05% of full-scale per °C after warm-up;
< 0.5% of full-scale per °C after warm-up
for expanded scales
Drift due to time < 0.01% of full-scale/hour after warmup
Noise < 6 mV peak-to-peak at the output,
measured with input open, 0.1 nA full-
scale gain, FINE GAIN fully clockwise
and 25°C ambient temperature (noise
Dynamic Response
equivalent to < 0.6 pA peak-to-peak).
Bandwidth DC to 15 Hz (2-pole Low-Pass Filter,
transitional Butterworth-Thompson)
Line rejection frequency < -45 dB in a 0.1 Hz band about the line
frequency
Output impedance
Output Capability
100Ω± 5%
Maximum output current ± 5 mA (minimum, short circuit)
Note: Higher output currents are available, but system accuracy is not guaranteed.

A-M Systems 131 Business Park Loop, P.O. Box 850 Carlsborg, WA 98324
17
Telephone: [phone] * 360-683-8300 * FAX: [phone]
E-mail: [e-mail] * Website: http://www.a-msystems.com
Warranty and Service
LIMITED WARRANTY
What does this warranty cover?
A-M Systems, LLC (hereinafter, “A-M Systems”) warrants to the Purchaser that the Instruments manufactured by A-
M Systems (hereinafter the “hardware”), and sold after January 1, 2020, is free from defects in workmanship or
material under normal use and service for the lifetime of the hardware. Headstages manufactured by A-M Systems
and sold after January 1, 2020, will be repaired under warranty only once per year. This warranty commences on the
date of delivery of the hardware to the Purchaser. “Lifetime” is defined as the time all components in the instrument
can still be purchased from mainstream, common, electronic component distributors such as Digi-Key Electronics,
Newark, or Mouser Electronics.
For hardware sold prior to January 1, 2020, the warranty in effect at time of purchase applies, with the maximum
warranty period of three (3) years for new purchases, and one (1) year for those that have been repaired by A-M
Systems. For headstages manufactured by A-M Systems and sold prior to January 1, 2020, the maximum warranty
period is one (1) year.
What are the obligations of A-M Systems under this warranty?
During the warranty period, A-M Systems agrees to repair or replace, at its sole option, without charge to the
Purchaser, any defective component part of the hardware. To obtain warranty service, the Purchaser must return the
hardware to A-M Systems or an authorized A-M Systems distributor in an adequate shipping container. Any postage,
shipping and insurance charges incurred in shipping the hardware to A-M Systems must be prepaid by the Purchaser,
and all risk for the hardware shall remain with Purchaser until A-M Systems takes receipt of the hardware. Upon
receipt, A-M Systems will promptly repair or replace the defective unit and then return the hardware (or its
replacement) to the Purchaser with postage, shipping, and insurance prepaid by the Purchaser. A-M Systems may use
reconditioned or like-new parts or units at its sole option, when repairing any hardware. Repaired products shall carry
the same amount of outstanding warranty as from original purchase. Any claim under the warranty must include a
dated proof of purchase of the hardware covered by this warranty. In any event, A-M Systems liability for defective
hardware is limited to repairing or replacing the hardware.
What is not covered by this warranty?
This warranty is contingent upon proper use and maintenance of the hardware by the Purchaser and does not cover
batteries. Neglect, misuse whether intentional or otherwise, tampering with or altering the hardware, damage caused