Keithley 7012-C, Instruction Manual, Page: 66 / 93

Service Information
5-4
1. Turn the Model 7001 off if it is on.
2. As shown in Figure 5-1, connect all terminals of
matrix columns 1-10 together to form one common
terminal.
3. Set the Model 196 to the 300
Ω
range and connect
four test leads to the OHMS and OHMS SENSE in-
put.
4. Short the four test leads together and zero the
Model 196. Leave zero enabled for the entire test.
5. Connect OHMS HI and OHMS SENSE HI of the
Model 196 to the common terminal. It is recom-
mended that the physical connections be made at
columns 1 and 10 as shown in the illustration.
6. Connect OHMS LO and OHMS SENSE LO to the
high (H) terminal of Row 1.
7. Install the Model 7012 in slot 1 (CARD 1) of the
Model 7001.
8. Turn on the Model 7001 and program it to close
Channel 1!1!1 (Slot 1, Row 1, Column 1). Verify that
the resistance of this channel is <1
Ω
.
9. Open Channel 1!1!1 and close 1!1!2. Verify that the
resistance of this channel is <1
Ω
.
10. Open Channel 1!1!2 and close 1!1!3. Verify that the
resistance of this channel is <1
Ω
.
11. Repeat the basic procedure of opening and closing
channels to check the resistance of Row 1 high (H)
terminal paths for Columns 4 through 10 (Chan-
nels 1!1!4 through 1!1!10).
12. Turn off the Model 7001 and connect the OHMS
LO and OHMS SENSE LO test leads of the Model
196 DMM to the low (L) terminal of Row 1.
13. Repeat steps 8 through 11 to check the low (L)
channel paths of Row 1.
14. Turn off the Model 7001 and repeat the basic proce-
dure in steps 7 through 13 for Rows 2, 3 and 4.
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 pathway. 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 Row 1 of
the matrix card as shown in Figure 5-2. Note that
electrometer HI is connected to both high (H) and
low (L) of Row 1. Electrometer LO is connected to
chassis ground, which is accessible at the rear pan-
el of the mainframe.
3. Install the matrix card in slot 1 (CARD 1) of the
Model 7001.
4. On the Model 617, select the 200pA range, and en-
able zero check and zero correct in that order.
Leave zero correct enabled for the entire proce-
dure.
5. Turn on the Model 7001
6. Program the Model 7001 to close Channel 1!1!1.
7. On the Model 617, disable zero check and verify
that it is <100pA. This measurement is the leakage
current of the pathway.
8. On the Model 617, enable zero check and on the
Model 7001, open Channel 1!1!1.
9. Repeat the basic procedure in steps 6 through 8 to
check the rest of the pathways (Channels 1!1!2
through 1!1!10) of the row.
10. Turn off the Model 7001 and connect the Model 617
to Row 2. Repeat the basic procedure in steps 6
through 9 to check Channels 1!2!1 through 1!2!10.
11. Repeat the basic procedure in step 10 to check
Rows 3 and 4.
12. Turn off the Model 7001.
13. To check differential offset current, connect the
Model 617 to Row 1 as shown in Figure 5-3, and re-
peat steps 4 through 12.
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