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Service Information
6-6
Contact potential tests
These tests check the EMF generated by each relay contact
pair (H and L) for each pathway. The tests simply consist of
using a sensitive digital voltmeter (Model 182) to measure
the contact potential (Figure 6-4).
Perform the following procedure to check contact potential
of each path:
1. Turn off the Model 7001/7002 if it is on.
2. Place a short between HI to LO on each input column
1-6.
3. Connect all row HI terminals together on the common
bus.
4. Connect all row LO terminals together on the common
bus.
5. Place a short between HI to LO on the rows.
6. Connect the Model 182 input leads to HI and LO of the
rows.
7. Install the Model 7022 in the Model 7001/7002 slot 1
and turn on the mainframe.
8. Allow the Models 7022, 7001/7002, and 182 to warm up
for two hours.
9. Select the 3mV range on the Model 182.
10. Press REL READING on the Model 182 to null out
internal offsets. Leave REL READING enabled for the
entire procedure.
11. Turn off the mainframe. Remove the Model 7022 front
slot 1. Cut the short from HI to LO on the rows.
12. Install the Model 7022 in the Model 7001/7002 slot 1
and turn on power.
13. Wait 15 minutes.
14. Program the Model 7001/7002 to close channel 1!1.
15. After settling, verify that the reading on the Model 182
is <3µV. This measurement represents the contact
potential of the pathway.
16. From the Model 7001/7002, open channel 1!1.
17. Repeat steps 14 through 16 for all 30 crosspoints.
Figure 6-4
Contact potential testing
A
B
C
1
3
4
5
6
2
Model 7022
HI
LO
Model 1484
Low Thermal Cable
(Unterminated)
Rows
Columns
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
D
H
L
E
H
L
KEITHLEY
182 SENSITIVE DIGITAL VOLTMETER
TRG
SRQ
REM
TALK
LSTN
Model 182
Low Thermal, short,
clean, high purity
copper (1 of 6)
Setup shown is configured
to test row A crosspoints
for contact potential.
Note:
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