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3.5.2 Input
Isolation
This test measures the leakage current between a channel's HI and LO
terminals.
1. Set up the equipment
as shown in Figure 3-3.
2. Set the scanner to channel 1 and the step mode. Close channel 1
and open all other channels.
3. Set the electrometer
to amps and zero check. Program the Model
230 to output
1OOV. Take the electrometer
out of zero check.
4. The electmmeter should read less than 10.'A. (Due to the capacitance
of the circuit,
the offset current
may be high until
the circuit
capacitance is charged up. Wait until the readings settle out.)
5. Using Ohm's law, calculate the input isolation
(leakage resistance)
for this channel.
For example:
R = E/l = IOOVilO-'A = IO'Q.
NOTE
With the Model 617 electrometer in VII mode, the resistance
is calculated automatically.
6. Put the Model 230 in standby mode and set the electrometer to zero.
7. Repeat steps 2 through
6 for the remaining
channels.
NOTE
For all other channels, the channel under test should be
closed and all other channels open.
22
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