Keithley 610B Instruction Manual page 17

MODELS bLOB, 61OBR ELECTROMETERS OPERATION
2-7. Resistance Measurements.
a. The Model 610B can measure resistances by three methods.
1.
In the normal or two-terminal method (annneter-voltmeter) , the ELec-
trometer measures the voltage drop across the unknown sample as a known,
constant current flows through it.
The voltage drop is proportional to
the resistance of the sample.
to LO11 ohm ranges.
This method is the simplest for the 100
2. Above LOLL ohms or to prevent leakage,
the guarded method is better.
It results in faster response speeds and also nullifies Leakage errors
across the Electrometer input, since the potential across the input ter-
minal is small.
3. In the preceeding methods,
the voltage across the sample cannot be
arbitrarily set.
In some cases,
as in measuring capacitor leakage, these
methods involve much more time than if a Larger voltage could be applied.
In the external voltage method the Model 6LOB Fs used as a fast picoammeter.
The unknown resistance sample is connected to an external known voltage
source and the current through the sample is measured,
Either the normal
or fast method may be used. The resistance is calculated from the readings.
NOTE
Discharge any capacitor before removing it from the circuit.
Depressing the ZERO CHECK Button shorts the fnput through a
lo-megohm resistor, providing a discharge path.
b. Normal Method (100 to 10" ohm ranges).
1. Follow the instructions of paragraph 2-4. Set the controls as follows:
METER Switch
Range Switch To5 OHMS
Multiplier Swftch 1
FEEDBACK Switch NORMAL
ZERO CHECK Button LOCK
Connect the resistance sample to the INPUT Receptacle. Unlock the ZERO
CHECK Button. Check zero with only the ZERO CHECK Button,
Do not open-circuit the Electrometer on the OHMS ranges; the
input will develop a Large voltage due to its constant current
characteristic. Keep the input shorted or the ZERO CHECK
Button locked.
2. The full-scale ohms range is the Range Switch setting times the
Multiplier Switch setting. Use the Largest Multiplier Switch setting
possible to obtain the best accuracy.
1064R
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