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5.3.5 Offset current tests
These tests check leakage current from high (H) to low
(L) (differential), and from high (H) and low (L) to
chassis (common mode) for each channel. In general,
these tests are performed by simply measuring the
leakage current with an electrometer. In the following
procedure, the Model 617 is used to measure leakage
current.
Referring to Figure 5-2, perform the following proce-
dure to check offset current:
1. Turn the Model 7001 off if it is on.
2. Connect the Model 617 electrometer to the input
(IN) of Channel 1 as shown in Figure 5-2A.
3. Install the switch card in slot 1 (CARD 1) of the
Model 7001 if it is not already installed.
4. On the Model 617, select the 200pA range, and
enable zero check and zero correct in that order.
Leave zero correct enabled for the entire
procedure.
5. Turn on the Model 7001
6. Program the Model 7001 to close Channel 1!1.
7. On the Model 617, disable zero check and verify
that it is <100pA. This measurement is the differen-
tial leakage current of the channel.
8. On the Model 617, enable zero check and turn the
Model 7001 off.
9. Connect the Model 617 electrometer to Channel 1
as shown in Figure 5-2B. Note that electrometer HI
is connected to both high (H) and low (L) of Chan-
nel 1 by using a jumper. Electrometer LO is con-
nected to chassis ground, which is accessible at the
rear panel of the mainframe.
10. Install the switch card in slot 1 (CARD 1) of the
Model 7001 if it is not already installed.
11. On the Model 617, select the 200pA range, and
enable zero check and zero correct in that order.
Leave zero correct enabled for the entire
procedure.
12. Turn on the Model 7001
13. Program the Model 7001 to close channel 1!1.
14. On the Model 617, disable zero check and verify
that it is <100pA. This measurement is the com-
mon-mode leakage current of the channel.
15. On the Model 617, enable zero check.
16. Repeat the basic procedure in steps 1 through 15 to
check the other channels. Remember to close the
channel that the electrometer is connected to.
5.3.6 Contact potential tests
These tests check the EMF generated by each relay con-
tact pair (H and L) for each channel. The tests simply
consist of using a sensitive DVM (Model 182) to mea-
sure the contact potential.
Perform the following procedure to check contact
potential of each path:
1. Turn the Model 7001 off if it is on.
2. As shown in Figure 5-3, short output (OUT) high
(H) to low (L) of Channel 1. The low thermal short
must be clean high purity copper.
3. Set the Model 182 to the 3mV range, short the input
leads and press REL READING to null out internal
offset. Leave REL enabled for the entire procedure.
4. Connect the Model 182 to a Channel 1 as shown in
the illustration.
5. Install the switch card in slot 1 (CARD 1) of the
Model 7001 if it is not already installed.
6. Turn on the Model 7001
7. Program the Model 7001 to close channel 1!1.
8. Verify that the reading on the Model 182 is <500nV.
This measurement is the contact potential of the
channel.
9. Repeat the basic procedure in steps 1 through 8 to
test the rest of the channels of the Model 7013.
Service Information
5-5
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