Service Information
5-6
5.3.6 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.
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-B, B-C, and C-D.
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
1-40).
5. Place a short between HI to LO on output Bank D (long
enough to cut with wire cutters).
6. Connect the Model 182 input leads to HI and LO output
Bank A using copper wires.
7. Install the Model 7015 in slot 1, and turn the Model
7001/7002 on.
8. Allow Models 7001/7002, 7015 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 Model 7001/7002. Remove the Model 7015
from slot 1. Cut the short on B and D output HI to LO.
12. Install the Model 7015 in the Model 7001/7002 slot 1,
and turn power on.
13. Wait 15 minutes.
14. Program the Model 7001/7002 to close Channel 1!1.
15. After settling, verify that reading on the Model 182 is
within required limits (see specifications). This mea-
surement represents the contact potential of the path-
way.
16. From the Model 7001/7002, open Channel 1!1.
17. Repeat steps 12 through 14 for all 40 channels.
Figure 5-3
Contact potential test connections
A
B
C
D
1
3
4
5
6
7
8
9
10
2
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
Bank
Outputs
Model 7015
HI
LO
Note : Setup shown is configured
to test Bank A thru D
relays for contact potential.
Model 1484
Low Thermal Cable
(Unterminated)
Low thermal short.
Clean high purity
copper (1 of 40)
KEITHLEY
182 SENSITIVE DIGITAL VOLTMETER
Model 182
Bank Inputs
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