Keysight DAQ970A Guide D'utilisation page 246

Two-wire multiplexers
The DAQM900A, DAQM901A, and DAQM902A multiplexers switch both HI and LO inputs, thus providing fully
isolated inputs to the internal DMM or an external instrument. These modules also provide a thermocouple reference
junction for making thermocouple measurements.
Four-wire multiplexers
You can make 4-wire ohms measurements using the DAQM900A, DAQM901A, and DAQM902A multiplexers. For a
4-wire ohms measurement, the channels are divided into two independent banks by opening the bank relay.
For 4-wire measurements, the instrument automatically pairs channel n with channel n+10 (DAQM901A) or n+8
(DAQM902A) to provide the source and sense connections. For example, make the source connections to the HI and
LO terminals on channel 2 and the sense connections to the HI and LO terminals on channel 12.
If any channels are configured to be part of the scan list, you cannot close multiple channels; closing one chan-
nel will open the previously closed channel.
When making a 4-wire measurement, the test current flows through the source connections from the HI terminal
through the resistor being measured. To eliminate the test lead resistance, a separate set of sense connections are
used as shown below:
Keysight DAQ970A/DAQ973A User's Guide
4 Measurement Tutorials
246