Keithley 7035, Инструкция по эксплуатации

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Service Information
5-4
Offset current tests
These tests check for leakage current between HI (H) and LO
(L) (differential offset current) and from HI (H) and LO (L)
to chassis (common-mode offset current) of each pathway. In
general, these tests are performed by measuring the leakage
current with an electrometer. In the following procedure, the
Model 6517A is used to measure the leakage current. Test
connections are shown in Figure 5-2.
Perform the following procedure to check offset current:
1. Turn off the Model 7001/7002 mainframe if it is on, and
remove any jumpers or wires connected to the card.
2. Connect the triax cable to the Model 6517A, but do not
connect it to the card at this time.
3. Turn on the Model 6517A and allow the unit to warm up
for two hours before testing.
4. After warm up, select the 200pA range, and enable zero
check and zero correct the instrument. Leave zero cor-
rect enabled for the entire procedure.
5. Connect the triax cable to bank A HI and LO, as shown
in A.
6. Install the Model 7035 in slot 1 (CARD 1) of the main-
frame.
7. Turn on the mainframe.
8. Program the unit to close channel 1!1 (bank A, input 1).
9. On the Model 6517A, disable zero check and allow the
reading to settle. Verify that the reading is <100pA. This
specification is the offset (leakage) current of the path-
way.
10. Enable zero check on the Model 6517A and open chan-
nel 1!1 from the front panel of the mainframe.
11. Repeat the basic procedure in steps 8 through 10 to
check the rest of the pathways (inputs 2 through 4) of
bank A (channels 1!2 through 1!4).
12. Turn off the mainframe and change the electrometer
connections to the next bank.
13. Repeat the basic procedure in steps 7 through 12 to
check bank B through I, (channels 1!5 through 1!36).
14. Turn off the Model 7001/7002 and change the electrom-
eter connections as shown in B. Note that electrometer
HI is connected to HI and LO of the bank A output,
which are jumpered together. Electrometer LO is con-
nected to chassis.
15. Repeat steps 7 through 13 to check that the common
mode offset current is <100pA.