3 Performance Verification
90 Keysight DAQ970A/DAQ973A Service Guide
DAQM908A relay contact resistance verification (optional)
This procedure checks the relay contact resistance for relays used in Channel 01
to 40 on the DAQM908A. It uses the internal DMM of the DAQ970A/DAQ973A to
make resistance measurements. To ensure accurate measurements, the
DAQ970A/DAQ973A has to be calibrated prior to this procedure.
1 Connect copper shorts from each channel to the L terminal.
2 Perform a 2-wire resistance measurement for each channel using the
DAQ970A’s/DAQ973A’s internal DMM. Ensure that all measurements are less
than 2 W.
DAQM908A shorted relay contact verification
This procedure uses an external DMM to make 2-wire ohms measurements across
all H terminals on the DAQM908A. As this is to verify open or shorts only,
measurement accuracy is not required, so a 2-wire ohms measurement with
handheld test probes is sufficient.
1 Open all channels on the module by performing a card reset. Remove the
module from the DAQ970A/DAQ973A mainframe.
2 Measure the resistance from the H terminal (far left in the row of input
terminals) to Channel 01 to 20 terminals. Ensure that they are “open” or more
than 10 MW.
3 Plug the module back into DAQ970A/DAQ973A mainframe. Set channel 21 to
“close”. Remove the module from the mainframe. K422 (indicated by Channel
99 in the front panel module simplified schematic) should connect the
Common H terminal (second terminal from the left) to bank 2.
4 Measure the resistance from the Common H terminal to CH22 to 40 terminals.
Ensure that they are “open” or more than 10 MW.
5 Plug the module back into the DAQ970A/DAQ973A mainframe again. Set
Channel 22 to “close”. Remove the module from the mainframe.
NOTE
Ensure that you have read the “Plug-in Module Test Considerations” on page 76.
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