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Service Information
Contact potential tests
These tests check the EMF generated by each relay contact
pair (H and L) for each pathway. The tests consist of using a
sensitive digital voltmeter (Model 182) to measure the con-
tact potential.
Referring to Figure 6-3, perform the following procedure to
check contact potential of each path:
1. Turn off the Model 7001/7002 if it is on.
2. Place jumpers between banks A and B.
3. Turn on the Model 182 and allow the unit to warm up to
achieve rated accuracy.
4. Place a short between HI to LO on each input (channels
1!1-1!30).
5. Place a short between HI to LO on output bank B (long
enough to cut with wire cutters).
6. Connect the Model 182 input leads to HI and LO on out-
put bank A using copper wires.
KEITHLEY
182 SENSITIVE DIGITAL VOLTMETER
Model 182
1
2
6
HI
A
LO
3
4
5
B
H
L H
L H
L
Note: Setup shown is configured
to test Bank A and B
relays for contact potential.
Figure 6-3
Contact potential test connections
6-6
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TRG
SRQ
REM
TALK
Low Thermal Cable
LSTN
Bank Inputs
17
21
7
11
12
16
8
9
10
13
14
15
H
L
H
L H
L H
L H
L H
L H
7. Install the Model 7021 in the Model 7001/7002 slot 1,
and turn on the mainframe.
8. Allow Models 7001/7002, 7021, 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 in-
ternal offsets. Leave REL READING enabled for the
entire procedure.
11. Turn off the mainframe. Remove the Model 7021 from
slot 1. Cut the short on bank B output HI to LO.
12. Install the Model 7021 in mainframe slot 1, and turn
power on.
13. Wait 15 minutes.
14. Program the mainframe to close channel 1!1.
15. After settling, verify that reading on the Model 182 is
<3 µ V. This measurement represents the contact poten-
tial of the pathway.
16. From the mainframe, open channel 1!1.
17. Repeat steps 14 through 16 for all 30 channels.
Model 1484
(Unterminated)
Low thermal short.
Clean, high purity
copper (1 of 30)
22
26
27
18
19
20
23
24
25
28
L H
L H
L H
L H
L H
L H
Model 7021
Jumpers
H
L
Bank
Outputs
29
30
H
L
L H
L H
L
Low thermal short.
Clean, high purity
copper (1 of 1)
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