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Cirris® CH2 Custom Instructions
“Cirris CH2” is a category of Custom Instructions. These test instruction require no external instruments
to make test measurements. Some of the test instructions in this category allow the CH2 tester to
emulate other test equipment in the marketplace.
Compliance Limited 2W Resistance
This test instruction is almost identical to the Compliance Limited 4W Resistance test instruction with a
few exceptions. With Compliance Limited 2W Resistance, source current is limited from 10 nanoamps to
1 amp. A standard 2-wire connection is made to the device under test. See the Cirris Website for the
differences between 2 and 4-wire Resistance testing. See the Compliance Limited 4W Resistance below
for more information.
Compliance Limited 4W Resistance
To determine the resistance of a wire or resistor the tester applies a known current. With the applied
current, the tester measures voltage drop to determine a resistance measurement. With normal wire and
component instructions the CH2 auto selects the source current in order to sense a voltage as large as
possible but not more than 2.5 volts to measure resistances. With the compliance limited instruction the
tester allows you to specify the source current. The compliance voltage is the maximum voltage the
tester can apply while attempting to make the resistance measurement.
If hipot is used during the test of the DUT, both points included in the Compliance Limited Instruction are
sourced or sunk simultaneously during hipot, ensuring that no current or voltage is placed across the
points.
Compliance Voltage
The compliance voltage may be set from 100 millivolts to 10 volts. The tester will not allow voltage to rise
above the compliance voltage when the source current is applied to make the resistance measurement.
Choose a compliance voltage that is safely below (or in compliance with) the DUT test specifications and
measurement tolerances. If source current is set to greater than 10mA, the minimum compliance voltage
is 1 volt.
Source Current
The source current may be set from 20 nanoamps to 2 amps. The tester will attempt to apply the current
across the specified test points. Use ohms law to determine an adequate source current setting at the
given compliance voltage. Higher current will cause higher voltage drop in the resistance measurement.
If compliance voltage is set at less than one volt, you cannot set the source current higher than 10mA.
Dwell Time
In the context of this custom instruction, dwell time refers to the time that the tester applies the source
current before making the resistance measurement. The dwell period allows the reading to settle. Dwell
can be set from 10 milliseconds to 10 seconds. If set to zero, the tester will automatically adjust the dwell
until a stable reading is obtained with a maximum dwell time of 50 milliseconds.
NPLC
NPLC stands for number of power line cycles. In the US and other countries AC line frequencies are at
60 hertz meaning one power line cycle equates to 16.67 milliseconds. European and other countries use
50 hertz line power where one power line cycle equates to 20 milliseconds. The NPLC setting allows you
to set the measurement period (which occurs after the dwell period) in number of power line cycles. The
tester will average the measurements made throughout the measurement period specified by NPLC
value. Specifying a larger value for test time will result in higher measurement stability and repeatability.
Long cables, long fixturing, and measuring higher DUT resistances create more susceptibility to AC noise
affecting the measurement reading. NPLC may be entered in terms of the actual cycles or kilocycles.
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