A-MSystems 2200 User manual

INSTRUCTION MANUAL
FOR
ANALOG STIMULUS ISOLATOR
MODEL 2200
Serial #__________
Date____________
A-M Systems, Inc.
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
Operating Instructions.......................................................................................................2
Examples and Applications...............................................................................................6
Monophasic Output Pulse...........................................................................................................6
Combing Two 2200’s For Increased Output................................................................................7
Problem Solving..........................................................................................................................8
Theory of Operation.........................................................................................................10
Specifications...................................................................................................................11
Warranty and Service ...................................................................................................... 14
Each Stimulus Isolator is delivered complete with:
Battery Charger
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.

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General Description
The Model 2200 Analog Stimulus Isolator is designed for a wide variety of applications. It
provides opto-electrical isolation for stimuli generated by a wide range of signal sources. The
signal is DC-coupled, and can take on any waveshape within its wide bandwidth. The input
signal voltage, scaled according to the Range switch setting, can result in an output as large
as 100V (or ±50V), and ±5mA. The output signal can be turned on and off by a digital Control
Gate. If for any reason the instrument cannot follow the input signal, an Error indicator lights.
The isolated output section is battery-powered and optically-coupled to the input section, for
the ultimate in clean isolation. The battery is adequate to provide full function for at least 8
hours of continuous use. An internal battery tester is provided. A charger is supplied, and an
oven-night charge cycle is all that is required to ready the 2200 for another day’s use. It is
easy to swap a freshly charged pair of batteries if extended use is necessary.
There are several features to make this instrument highly useful in a computer-driven
environment via the Control port. The instrument is well suited to accepting analog signals
generated under computer control, isolating these signals from the noisy electrical
environment associated with a computer, and coupling them to biological tissue. The error
detection circuitry generates a TTL-level Control Error signal if the instrument is unable to
deliver the required signal. It is also possible to detect a low battery condition at any time,
without altering the isolation or interrupting an ongoing experiment.
NOTE
The 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.
WARNING the Model 2200 can produce potentially dangerous voltages (up to 100V) at
the output. The isolated output is not connected internally to safety (earth) ground in any
way. Some part of the external circuit should be connected to safety ground. Use
caution in handling any wires, connectors, or electrodes which may be directly or

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indirectly attached to the Model 2200 output. Some kinds of connectors (e.g. BNC
connectors) have exposed metal parts which may float at dangerous potentials unless
externally connected to safety ground. For greatest safety, turn the Model 2200 off
before handling connections to the output.
Operating Instructions
The instrument is very simple to operate. First, check the battery condition: set the Power
switch to off, and push the Battery Test button. The Test light should come on, indicating an
adequate charge. Connect your input signal to the Signal In connector. Set the Polarity
control to the predominant polarity of the waveform. Connect the Output to the stimulation
electrode (or other load you wish to drive) and set the Range switch to the correct scale. If
you wish to tum the output signal on or off by a separate controller (e.g. a timing signal), or be
able to test the batteries via computer control during the course of an extended experiment,
connect the control signal to the Control/ Gate input. Now tum the Power switch to On.
The output may go to an unpredictable state if the battery charge is not maintained. It is the
user’s responsibility to ensure an adequate battery charge. Regular use of either front-panel
or control-port battery testing is sufficient to guarantee proper battery charge.
The Error indicator should remain unlit in normal operation. The Error LED will light when the
computer-interface battery test is in operation. Be aware, however, that the Error LED will not
light if the batteries are dead! It is normal for the LED to turn on briefly when the front panel
controls are switched.
To recharge the batteries, connect the battery charger to the rear Charger input, and set the
Power switch to Charge. Note that if the switch is left in the Charge position without any
incoming electrical power, the batteries will very slowly, but certainly, become discharged.
Signal Control
The voltage at the Signal In BNC defines the output waveform. The signal is DC coupled
across the optical isolation barrier, so virtually any waveform can be used. It can be turned
on and off with a digital Gate signal through the Control port
Set the Range control to achieve the type (voltage or current) and amplitude of output
required. The output power is limited to 100V (±50V in bipolar mode) and ±5mA. For

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applications requiring the highest voltages (for example, trying to push “large” currents
through high resistance electrodes), it may be necessary to set the Polarity switch to the
dominant polarity of your signal. For most users, it should be necessary to set the Polarity
switch to the dominant polarity of you signal. For most users, it should be adequate to leave
the switch set to Bipolar, giving equal range for both positive- and negative-going signals.
For the most challenging cases, you may double the output power by combining two units.
For users requiring the lowest possible offset voltage or current, it maybe necessary to
readjust the Offset. Use the small insulated screwdriver (supplied with the Model 2200) to
zero the output while the input voltage is set to zero. It is best to do this with the Range
switch set to the desired position.
Battery Testing and Maintenance
There are two batteries: a small 9V “transistor” NiMH battery used to power the input section;
and a larger gelled-electrolyte 12V battery used to power the output. Both are rechargeable.
The internal batteries are designed to last at least 8 operating hours from a full charge. Brand-
new batteries often have a slightly reduced capacity, which improves after a few charge-
discharge cycles.
There are two methods to test the state of the batteries. From the front panel, simply turn the
Power to Off, and push the Battery/Test push-button. The Battery/OK LED will light if both
battery voltages are sufficiently high. Warning: this light does not indicate how long the
charge will remain high It is up to the user to maintain the battery charge properly.
To preserve maximum battery life, use the full battery capacity. Do not routinely discharge the
battery completely as the gelled-electrolyte (12V) battery life will eventually deteriorate if you
discharge it too far. At the other extreme, do not frequently discharge the batteries to a small
fraction of their capacity: shallow discharging of the unit may lead to diminished charge life of
the input-side (9V) battery.
If battery charge life is a problem, the simplest solution is to keep on hand a supply of one or
more sets of fully charged replacement batteries in addition to the internal set. - It is easy to
change the batteries: turn the Power switch Off, turn the unit upside-down, and unscrew the
two recessed Phillips head bolts (see figure 1). While holding the unit together, turn the unit
right-side up. The top side of the case comes off with an easy vertical pull. The 9V battery is
in a battery holder on the horizontally-mounted circuit board; simply pry the discharged unit
out (pull on the attached tab), and replace with another battery. Disconnect the wire from the
larger 12V battery at the connector to the circuit board. Now pull the battery from the Velcro®
pad that it is sitting on. Replace the battery, making sure that it is firmly pressed into the pad.
Reconnect the new battery to the circuit board, making certain that the keyed connector is
locked together with the correct orientation! If the connector does not go together easily, you
may have it upside-down. Reinstall the top cover and tighten the two bolts. Pushing the Test
push button should now light the Battery OK LED.

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NOTE: If the Model 2200 is beeping, then the 9V battery needs to be replaced.
Figure 1. Bottom view of case: screw locations
If for some reason it is necessary to store the 2200 for more than a few months, it is
recommended that the unit be kept at a low temperature(5-10°C). Before storing for longer
than a year, it is advisable to remove the batteries from the unit; store the batteries separately
Control Port
Digital control is performed via the subminiature DB-9 connector on the instrument.
Signal Description
The output signal is turned on and off via the Gate line. The default (open circuit) condition is
a logical “1”, allowing unimpeded signal transmission from input to output.
Output errors may be detected via the Error line. Normally at a logical “0”, this line goes high
for at least 500ms if the output amplifier cannot drive the load satisfactorily or if the output
range were exceeded, such as trying to obtain 200V from the unit.
Since it is possible that either or both of the internal batteries will be too low to provide a
readable Error signal, it is strongly recommended that a periodic battery check be done via the
front panel button in order to ensure proper operation.
Pinout
The pins are connected as follows. Note that while this is mechanically compatible with a 9-
pin RS-232 connector, it is not electrically compatible. The 2200 is not smart enough to
understand serial communications; and for some, the slow, erratic speed of serial
communications would compromise performance

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Pin Number In/Out Pin Name
1 O Battery OK
2 O Output Error
3 Ground
4 I Gate
5 O VCC (do not connect to any other device)
6 I Battery Test
7 Ground
8 No Connection
9 No Connection
All signals are active-high.
The accessory cable #851000 gives a connection to the Gate signal (and ground) only
Do not connect the Battery/Test signal permanently low: this would reduce battery charge
life, and prevent real output errors from being detected. Do not connect anything to pin 5
of DB-9 connector without consulting A-M Systems, or its representative.

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Examples and Applications
The first thing that should be done in any use of this instrument is to check the batteries
using the internal battery test function. Set the Power switch set to Off, and push the
Battery/Test push-button. The Battery OK light should come on, indicating an adequate
charge. If the test light does not come on, the batteries need to be recharged. The
following applications assume that this simple test has been passed first.
Monophasic Output Pulse
An example of a simple application (and basic instrument test) is using a pulse generator,
function generator, or other source of TTL-compatible voltages to provide an On/Off signal.
Control/Connector Setting
Output Connect a 10kohm resistor to the output
Connect an oscilloscope probe across the resistor.
Input Connect a function generator with a 1kHz 1V p-p sine wave
Sign Bipolar
Range 1V/V
Power On
You should observe the same waveform on both input and output. Rotating the DC offset
control on the function generator should cause the DC level to change equally in input and
output.
Change the Range control to 1mA/V. The waveform should stay the same. Now turn the
Power off, disconnect the 1kWresistor, and turn the Power back on. The output waveform
should be much larger (flattening against the power supply rails), and the error LED should
light up as the 2200 fails to drive up to 6500mA into the high impedance of the oscilloscope
input/load.

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Combing Two 2200’s For Increased Output
If you require up to twice the maximum output voltage, connect two 2200 units in a series.
If you require up to twice the maximum current of a single 2200, connect the 2200’s in
parallel. The Gate inputs may be connected (and driven) together, by the same timing
source.

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Problem Solving
If the instrument appears to be not working properly, check all of the control settings and
connections. The following brief summary of typical problems for the user (along with the
most common solutions may help:
The Instrument is beeping
No output (and the Error LED does
Replace the 9V battery and reset the
alarm button on the rear panel
• One or both of the batteries are
not light).
uncharged (test batteries: recharge as
required.
• The Gate input is held low
(must be high for an output to occur).
Battery OK LED does not light when
• Power switch is not set to Off (set to Off).
pressing Test.
• One or both of the batteries need
recharging.
Battery OK LED does not light, but
• This indicates that the batteries are
Battery OK and Error signals of port
almost fully discharged. The front panel
test positive.
battery test requires a slightly greater
battery level to operate successfully.
Error LED on, even with no input
• Low batteries (recharge).
Error LED lights when Gate is turned
• Excessive drive: Unit is limited to ±
100V in monopolar mode or ± 50V in
bipolar mode (reduce input drive or gain).
on
• Current mode: load is disconnected
(check wiring); or load impedance is too
high for limited output voltage capability
(cascade more than one unit).
• Battery charge is low (recharge)
• Gate signal erroneously connected to
Battery Test input (change connection).
Error LED lights when Battery Test signal
is used
• This is normal.
Excessive noise on the output
• Charger is still plugged in (unplug/
disconnect.
• In the lowest current range: stray
electrical interference can degrade noise
performance if it mostly couples into the

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output pin. (Try operating the 2200 within
a Faraday (electrostatic shielding) cage.
Match or reduce the stray capacitance to
each output pin. Shorted the output
connections. If these are inadequate,
reverse the output banana connector, and
invert the signal polarity).
If you suspect the Model 2300 may have failed, we recommend checking the basic level of
functionality. If the instrument fails at this basic level, the instrument is defective and must
be recalibrated or repaired.

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Theory of Operation
The operation of the Model 2200 is summarized in the block diagram (see Fig. 4). The input
signal is buffered, then enabled or disabled by an analog gate. When disabled, the output
voltage at this stage is zero. A linear optoisolator system is used to couple the signal to the
isolated section. The isolated signal is amplified (and possibly converted to a current)
according to the Range setting.
The output amplifier is connected as a voltage-gain amplifier in voltage modes, with different
feedback resistances depending on the setting. In the current mode, the same amplifier is
used to fix a virtual ground within the instrument. The two currents connected to this virtual
ground are the set current, determined by the range switch and input signal amplitude; and
the load, driven by the amplifier output
Figure 4. Instrument block diagram
With the Control Gate input signal open (disconnected), or set to a logical I by an external
signal, the signal propagates normally as described above. If the Gate is set to a logical 0, the
internal signal is connected to the input ground instead of the input signal.
Output errors are measured by sensing the output amplifier’s differential input voltage. If for
any reason the amplifier fails to deliver the requested signal, a warning LED illuminates and
the Error output pin is set to a TTL-high level.
Two sets of batteries are used to power the 2200. Note that the BATTTERY tester only detects
the present state of the batteries, and does not indicate how long the charged batteries will be
able to support the load. The batteries used in the 2200 vary more from unit to unit than from
fullly-charged to nearly-discharged, making it impractical to measure the charge state. It is
recommended that you, the user, keep track of battery usage to ensure that the battery does
not become exhausted at a critical time.

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Specifications
There are three classes of specifications. Class A specifications are tested in all units,
and are guaranteed. Class B specifications are inherent in the design; they are indirectly
tested, and are guaranteed. Class C specifications are typical operating values which are
occasionally tested; these are typical values, given for your information but not
guaranteed. The class for each specification is noted in the center column of the following
sections. All specifications require that the batteries are adequately charged, and the
instrument if fully warmed up (at least 15 minutes).
Input
Input resistance
B
1 Mohm ± 1% in parallel with
less than 22pF
Logical ‘0’
B
<0.8 V
Logical ‘1’
B
>2.4 V
Input equivalent circuit
C
>33ohms in parallel with no more
than 35pf
Maximum linear input
B
±10V
Signal Input to output delay
C
≈5µs for a load of more than
100kohms in parallel with 50pF
Control timing jitter
C
<0.1µs
Gate polarity
A
active high (default is high = on)
Gate to output delay
C
≈6µs
Battery Test polarity
A
active high (default is low = off)
Battery Test to output delay
C
<0.1 ms (turning on); < 1 sec
Outputs
(turning off)
Maximum output capability
A
±50 V Bipolar (+ polarity) or
±100V Monopolar. (-
polarity) ±5mA. Both limits
apply to all Range settings.
Full scale output
B
±10V x Range setting
Gain
A
Within ±3% of setting at DC.
Accuracy is reduced for high

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output currents in voltage
modes, to ±2% at full output
.
Transient response
A
<10µs risetime into
1megohm (10 kohm in
current modes) in parallel
with less than 47pF.
Decreases to ≈4 µs with
jumper J350 removed.
Bandwidth
B
Within 1-3 dB from DC to
40kHz (same load
impedances as above.
Increases to ≈100kHz by
removing jumper J350.
Maximum Slew rate (the effective
bandwidth is reduced for large
signals) with 10kohm and 20pF
load.
C
RANGE SLEW RATE
10V/V 5V/ µs
1V/V 0.6V/ µs
1mA/V 0.4mA/ µs
0.1mA/V 54µA/ µs
10µA/V 5.6µA / µs
10A /V 0.6µA / µs
Note: Risetime in current modes is slower than in voltage modes if the wiring
capacitance approaches or exceeds 4.5 x 106R-1pF (R in ohms). Bandwidth is
decreased by the same factor. This is a function of the load impedance driven by a
constant current source, not a static property specific to the Model 2200.
Offset
A
within ±0.002% of full scale
(plus additional ±1nA offset in
current modes) at 25°C .
Drift
B
Less than ±0.01% of full
scale per °C from 10 to 30°C
Output impedance C
RANGE SLEW RATE
10V/V ≈50 ohms
1V/V ≈50 ohms
1mA/V >1gigohm
10µA/V >50gigohm

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1µA /V >50gigohm
Noise, typical (voltage modes: C
MODE
RMS % FULL SCALE
open circuit load; current modes:
10V/V
<10mV 0.01
100kohm load) 10 Hz - 100 kHz
1V/V
<3mV 0.03
bandwidth. J350 in place
1mA/V
<1µA 0.01
0.1mA/V
<100µA 0.01
10µA/V
<10nA 0.01
1µA/V
<2na 0.02
Isolation resistance A
>>200Mohms
Isolation capacitance C
<20pF
Overload error
C
Flat to approx. 10ms duration
Decreasing sensitivity for
shorter pulses.
Miscellaneous
Battery load life (from full
charge)
B
At least 8 hours (Control/Battery
Test on less than 100 seconds,
total)
Battery charge time
B
No more than 14 hours
Battery charge life (unit off)
B
At least 2 months
Operating temperature
range
10-30°C
Operating humidity
5-80% RH
Storage temperature range
0-40°C
Dimensions
6.35 cmH x 15.4 cmW x 15.9 cmD
Weight
1.15kg

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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 by
accident, damage caused by unusual physical, electrical, chemical, or electromechanical stress, damage caused by failure of
electrical power, or damage caused during transportation are not covered by this warranty. Further, no guarantee is made
regarding software compatibility with future updated operating systems. Products may not be returned to A-M Systems for
service, whether under warranty or otherwise, which are contaminated by infectious agents, radioactive compounds or other
materials constituting a health hazard to employees of A-M Systems

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LIMITED WARRANTY, cont
What are the limits of liability for A-M Systems under this warranty?
A-M Systems shall not be liable for loss of data, lost profits or savings, or any special, incidental, consequential, indirect or
other similar damages, whether arising from breach of contract, negligence, or other legal action, even if the company or its
agent has been advised of the possibility of such damages, or for any claim brought against you by another party.
THIS EQUIPMENT IS NOT INTENDED FOR CLINICAL MEASUREMENTS USING HUMAN SUBJECTS.
A-M SYSTEMS DOES NOT ASSUME RESPONSIBILITY FOR INJURY OR DAMAGE DUE TO MISUSE OF
THIS EQUIPMENT.
Jurisdictions vary with regard to the enforceability of provisions excluding or limiting liability for incidental or
consequential damages. Check the provision of your local jurisdiction to find out whether the above exclusion applies to
you.
This warranty allocates risks of product failure between the Purchaser and A-M Systems. A-M Systems hardware pricing
reflects this allocation of risk and the limitations of liability contained in this warranty. The agents, employees, distributors,
and dealers of A-M Systems are not authorized to make modifications to this warranty, or additional warranties binding on
the company. Accordingly, additional statements such as dealer advertising or presentations, whether oral or written, do not
constitute warranties by A-M Systems and should not be relied upon. This warranty gives you specific legal rights. You
may also have other rights which vary from one jurisdiction to another.
THE WARRANTY AND REMEDY PROVIDED ABOVE IS IN LIEU OF ALL OTHER
WARRANTIES AND REMEDIES, WHETHER EXPRESS OR IMPLIED. A-M SYSTEMS
DISCLAIMS THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR USE, WITHOUT LIMITATION.

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A-M Systems Model 2200 Manual DRW-5027300 rev 9
Revision History
Rev Date Description
81/18/19 DCR 202615 Review content, add content rev control.
93/19/20 DCR 203316. Update warranty.