NI switch modules are capable of switching one, two and/or four wires.

1-Wire

In 1-wire mode, you connect the HI leads to the relays and the LO leads to a common connection. All signals are referenced to this common connection. All NI multiplexers can operate in 1-wire mode. The following figure shows an example of 1-wire mode.

2-Wire

In 2-wire mode, you connect both positive and negative leads to the terminals of a channel. The following figure shows an example of 2-wire mode.

4-Wire

4-wire mode is usually used for 4-wire resistance measurements. One channel (two leads) is used for the current excitation and another channel (two leads) is used for measuring the voltage drop (sense) across the resistor. The following figure shows an example of 4-wire mode.