Keithley 600A Instruction Manual page 21

MODEL 6oOA ELXC!CBOMEZER CIRCUIT DISCUSSION
drop divided by the current measured. It will be rarely necessary
to correct for the input drop of the electrometer due to the excel-
lent voltaRe sensitivity of the Model
600~.
It is advisable to use the NOW micro-microammeter connection
for the measurement of leakage resistance of capacitors in this
manner, since instability is likely to occur using the FAST con-
nection.
However, in cases where the capacity shunted across the
sample is small, it will be possible to realize a considerable
increase in speed of response by utilizing the FAST connection.
Some precautions are recommended when testing capacitors. Be sure
that capacitors have discharged before removing from test circuit.
With the ZERO CHECK switch depressed,the input is shorted to
ground through 1 megohm, providing a discharge path for the cana-
citor. The reading: time may be shortened if the capacitor is al-
lowed to charge through a low impedance position on the AMPERES
switch before the appropriate measuring resistor is inserted in
the circuit.
It should be further noted that capacitor measurement is likely
to be a slow process in any case due to the fact that it may take
considerable time for the molecular orientation of the dielectric
to take place at the testing potential. It may take minutes or
even hours in some cases to achieve a stable reading.
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