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5.3.8 Differential and common-mode isola-
tion tests
These tests check the leakage resistance (isolation) be-
tween high (H) and low (L) (differential), and from
high and low to chassis (common-mode) of every row
and column. In general, the test is performed by apply-
ing a voltage (100V) across the terminals and then mea-
suring the leakage current. The isolation resistance is
then calculated as R = V/I. In the following procedure,
the Model 617 functions as a voltage source and an am-
meter. In the V/I function, the Model 617 internally cal-
culates the resistance from the known voltage and
current levels, and displays the resistance value.
1. Turn the Model 7001 off if it is on.
2. Connect the Model 617 to Row 1 as shown in Fig-
ure 5-6. Make sure the voltage source is in standby.
Also, make sure there are no other connections to
the card.
3. Install the Model 7012 in slot 1 of the Model 7001.
WARNING
The following steps use high voltage
(100V). Be sure to remove power
from the circuit before making con-
nection changes.
4. On the Model 617, select the 2pA range, and enable
zero check and zero correct in that order. Leave
zero correct enabled for the entire procedure.
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5. On the Model 617, set the voltage source for +100V,
and select the 200nA current range. Make sure the
voltage source is still in standby.
6. Place the Model 617 in the V/I measurement func-
tion by pressing SHIFT OHMS.
7. Turn on the Model 7001, but do not program any
channels to close. All channel crosspoints must be
open.
8. On the Model 617, disable zero check and press
OPERATE to source 100V.
9. After allowing the reading on the Model 617 to set-
tle, verify that it is >1G Ω . This measurement is the
leakage resistance (isolation) of Row 1.
10. Place the Model 617 in standby and enable zero
check.
11. Program the Model 7001 to close Channel 1!1!1.
12. On the Model 617, disable zero check and press
OPERATE to source +100V.
13. After allowing the reading on the Model 617 to set-
tle, verify that it is also >1G Ω . This measurement
checks the isolation of Column 1.
14. Using Table 5-3 as a guide, repeat the basic proce-
dure in steps 10 through 13 for the rest of the col-
umns and rows (test numbers 3 through 14 of the
table).
15. Place the Model 617 in standby and turn the Model
7001 off.
16. For each matrix row, jumper the high (H) terminal
to the low (L) terminal as shown in Figure 5-7.
17. Connect the Model 617 to Row 1 as shown in Fig-
ure 5-7, and repeat steps 7 through 15 to check
common-mode isolation.
Service Information
5-9
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