Contact Potential Tests - Keithley 2000-SCAN-20 Instruction Manual

4-6 Service Information

Contact potential tests

These tests check the EMF (contact potential) generated by each relay contact pair (HI and
LO) for each channel. The tests use a sensitive digital voltmeter (Model 182) to measure the
contact potential.
Perform the following procedure to check contact potential of each channel.
NOTE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Figure 4-2
Connections for contact potential tests
Connect bare copper jumpers between
HI and LO of each channel
Channel 1
Channel 2-9
Channel 10
Channel 11
Channel 12-19
Channel 20
To perform this test, you must custom-wire a cable to connect to the scanner card
connections.
Connect 1 in. #22AWG bare copper jumper wires between the HI and LO inputs of each
channel (Figure 4-2).
Connect the Model 182 Sensitive Digital Voltmeter to OUT A HI and LO using the low-
thermal cable (Figure 4-2).
With the power off, install the scanner card in the Model 2000-20 Multimeter.
Turn on the multimeter and the voltmeter. Allow the voltmeter to warm up for two hours
before taking measurements.
Select the 3mV range on the voltmeter.
Select the DCV function on the multimeter.
Program the multimeter to close channel 1.
Verify that the voltmeter reading is <2µV.
Repeat steps 7 and 8 for all 20 channels.
After completing all measurements, turn off the multimeter power, remove the scanner
card, and disconnect all jumpers and test leads.
HI
LO
HI
LO
4-Pole
HI
LO
HI
LO
Model 2000-SCAN-20
KEITHLEY 182 SENSITIVE DIGITAL VOLTMETER
TRG
SRQ
REM
TALK
LSTN
Model 182
HI
OUT A
LO
HI
OUT B
LO
2-Pole
Model 1484
Low-Thermal Cable
(Unterminated)