Solution
If the RTD connections on a Temperature Input module are shorted or left open, the temperature reading will be abnormally low or high respectively. It is not possible to predict the exact temperature readings since this will vary depending on the RTD type and measurement conditions.
Most Temperature Input modules will require that the RTD is connected between the RTD+ and RTD- pins. 4-wire RTDs require an additional excitation connection. The image below is an example of an RTD connection for a NI-9217 module. Review the specifications sheet for your device to understand the required connections.
RTDs will vary electrical resistance with temperature linearly, where lower resistances correspond to lower temperatures and vice versa. The RTD's nominal resistance is often used as the reference point for 0 °C.
Note: the nominal resistance varies depending on the type of RTD used. For platinum thin-film RTDs, nominal resistances include 100 Ω and 1000 Ω.
If the RTD pins on the Temperature Input module are shorted, this effectively acts as 0 Ω. Therefore, the temperature measurement will be less than -100 °C.
If the RTD pins are left open, this effectively acts as infinite Ω. Therefore, the temperature reading will be greater than 100 °C.