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