Keithley 7017, Instruction Manual

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Servicing
4-4
4.3.4 Isolation tests
Isolation tests check the leakage resistance (isolation) be-
tween various Model 7017 terminals using the ohms func-
tion of a Model 6517 Electrometer.
CAUTION
The following tests use the Model 6517
voltage source to measure resistance. Do
not apply more than 42V to the Model
7017 to avoid card damage.
Channel isolation tests
Perform the following steps to check channel isolation:
1. Connect the Model 6517 Electrometer to the center con-
ductors of channels 1 and 2, as shown in Figure 4-2.
2. With the power off, install the Model 7017 card in the
mainframe.
3. Turn on the mainframe and the Model 6517 power, and
allow the electrometer to warm up for at least one hour
before making measurements. Make sure the voltage
source is turned off.
4. Select the Model 6517 ohms function, choose the 2G
Ω
range, and make sure zero check is disabled.
5. Close channel 1 on the Model 7017.
6. Program the Model 6517 voltage source for 40V, and
make sure the internal voltage source connection mode
is selected.
7. Turn on the Model 6517 voltage source, and allow the
reading to settle.
8. Verify that the Model 6517 resistance reading is >1G
Ω
.
9. Turn off the voltage source, and open channel 1.
10. Repeat the procedure for channels 2 through 4, measur-
ing the resistance between the center conductor of each
channel and the center conductors of all other channels
of multiplexer A. For each test:
• Connect the electrometer to the center conductors of
the two channels being tested.
• Close only one of the channels being tested.
11. Repeat the entire procedure to test channel isolation be-
tween all multiplexer B channels (channels 5 through 8).
Center-to-shield isolation
Perform the following steps to check center-to-shield isolation:
1. Connect the Model 6517 Electrometer to the center con-
ductor and shield of channel 1, as shown in Figure 4-3.
2. With the power off, install the Model 7017 card in the
mainframe.
3. Turn on the mainframe and the Model 6517 power, and
allow the electrometer to warm up for at least one hour
before making measurements. Make sure the voltage
source is turned off.
4. Select the Model 6517 ohms function, choose the 2G
Ω
range, and make sure zero check is disabled.
5. Close channel 1 on the Model 7017.
6. Program the Model 6517 voltage source for 40V, and
make sure the internal voltage source connection mode
is selected.
7. Turn on the Model 6517 voltage source, and allow the
reading to settle.
8. Verify that the Model 6517 resistance reading is >1G
Ω
.
9. Turn off the voltage source, and open channel 1.
10. Repeat the procedure for channels 2 through 8, measur-
ing the resistance between the center conductor and
shield of each channel. For each test:
• Connect the electrometer to the center conductor and
shield of the channel being tested.
• Close only the channel being tested.
Multiplexer-to-multiplexer isolation
Perform the following steps to check multiplexer-to-multiplexer
isolation:
1. Connect the Model 6517 Electrometer to the center con-
ductors of channels 1 and 5, as shown in Figure 4-4.
2. With the power off, install the Model 7017 card in the
mainframe.
3. Turn on the mainframe and the Model 6517 power, and
allow the electrometer to warm up for at least one hour
before making measurements. Make sure the voltage
source is turned off.
4. Select the Model 6517 ohms function, choose the 2G
Ω
range, and make sure zero check is disabled.
5. Close channels 1 and 5 on the Model 7017.
6. Program the Model 6517 voltage source for 40V, and
make sure the internal voltage source connection mode
is selected.
7. Turn on the Model 6517 voltage source, and allow the
reading to settle.
8. Verify that the Model 6517 resistance reading is >1G
Ω
.
9. Turn off the voltage source, and open channels 1 and 5.