National Instruments NI 9217 - Manual (Page 8)

NI 9217 Operating Instructions and Specifications 8 ni.com
You can connect any combination of 3-wire or 4-wire RTDs to
the NI 9217. Each NI 9217 channel contains circuitry that
automatically detects the type of RTD connected to the channel.
The NI 9217 scans all four input channels and automatically
configures each channel for the appropriate mode. In 4-wire mode,
the EX terminal is a 1 mA current source. In 3-wire mode, the
RTD+ terminal is a 1 mA current source. The NI 9217
compensates for the error that lead resistance causes in 3-wire
mode. Refer to Figure 3 for an example of the input circuitry for
one channel of the NI 9217 in 4-wire mode.
Note You must use 2-wire ferrules to create a secure
connection when connecting more than one wire to a
single terminal on the NI 9217.
The NI 9217 channels share a common ground that is isolated from
other modules in the system. Each channel is filtered and then
sampled by a 24-bit analog-to-digital converter (ADC).