Keithley 6521, Instruction Manual, Page: 48 / 65

Service Information
4-6
4.3.7 Isolation tests
These tests check the leakage resistance (isolation) between
all Model 6522 channel input HI and LO terminals, and the
input isolation between the HI and LO terminals of each
channel. In general, the test is performed by applying a volt-
age from the Model 6517 voltage source across the terminals
and then measuring the isolation resistance using the ohms
function of the electrometer.
NOTE
The isolation tests covered here should be
performed only on the Model 6522 Scan-
ner Card. Isolation values for the Model
6521 Scanner card are not specified
Channel isolation
Perform the following steps to check channel isolation:
1. With the power off, install the scanner card in the elec-
trometer OPTION SLOT.
2. Turn on the Model 6517 power, and allow the unit to
warm up for at least one hour before making measure-
ments. Make sure the voltage source is turned off.
WARNING
The following steps use high voltage. Be
sure to turn off the Model 6517 voltage
source before making connection
changes.
3. Select the Model 6517 ohms function, choose the 20T Ω
range, and make certain zero check is disabled.
4. Connect the Model 6517 to the channels 1 and 2 HI in-
put terminals, as shown in Figure 4-4.
5. Press the OPTION CARD button, use the CHANNEL-
CLOSURES menu to close channel 1. Program the volt-
age source for 200V, and then turn on the Model 6517
voltage source.
6. Verify that the Model 6517 resistance reading is >10T Ω .
7. Turn off the voltage source, and open channel 1.
8. Repeat steps 6 through 8 for channels 2 through 10.
(Measure resistance between each channel in succession
and all other channels.)
9. Repeat the entire procedure for channel LO input
terminals.
Input isolation
Perform the following steps to check input isolation:
1. With the power off, install the scanner card in the elec-
trometer OPTION SLOT.
2. Turn on the Model 6517 power, and allow the unit to
warm up for at least one hour before making measure-
ments. Make sure the voltage source is turned off.
WARNING
The following steps use high voltage. Be
sure to turn off the Model 6517 voltage
source before making connection
changes.
3. Select the Model 6517 ohms function, choose the 20G Ω
range, and make certain zero check is disabled.
4. Connect the Model 6517 to the channel 1 HI and LO in-
put terminals, as shown in Figure 4-5.
5. Press the OPTION CARD button, use the CHANNEL-
CLOSURES menu to close channel 1. Program the volt-
age source for 200V output, and then turn on the Model
6517 voltage source.
6. Verify that the Model 6517 resistance reading is
>10G Ω .
7. Turn off the voltage source, and open channel 1.
8. Repeat steps 5 through 7 for channels 2 through 10.
(Measure resistance between HI and LO of each channel
with that channel closed.)