Connecting 3-Wire And 4-Wire Rtds - National Instruments NI 9217 Getting Started Manual

Signal
COM Common reference connection to isolated ground
EX Excitation source connection
RTD+ Positive resistance temperature detector connection
RTD- Negative resistance temperature detector connection

Connecting 3-Wire and 4-Wire RTDs

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.
12 | ni.com | NI 9217 Getting Started Guide
Table 1. Signal Descriptions
Description