Connection of resistance thermometers in 2-wire \ configuration

When resistance thermometers (Pt100, Pt1000, Ni1000, Cu50) are used, a constant current must flow through them to build the necessary voltage drop for the evaluation. For this, the module AI531 provides a constant current source which is multiplexed over the 4 analog channels.

The following figure shows the connection of resistance thermometers in 2-wire configuration.

Connection of resistance thermometers in 2-wire configuration. 1 analog sensor requires 1 channel.

The following measuring ranges can be configured AI531 Analog Input Module AI531 Analog Input Module:

Pt100	-50 °C … +70 °C / +400 °C; -200 °C … +850 °C	1 channel used
Pt1000	-50 °C … +400 °C	1 channel used
Ni1000	-50 °C … +150 °C	1 channel used
Cu50	-50 °C … +200 °C (1.426); -200 °C … +200 °C (1.428)	1 channel used

The function of the LEDs is described under Diagnosis and displays / displays AI531 Analog Input Module.

The module linearizes the resistance thermometer characteristics.

In order to avoid error messages from unused analog input channels, it is useful to configure them as “unused”.