Connection of Resistance Thermometers in 2-wire Configuration

When resistance thermometers (Pt100, Pt1000, Ni1000) are used, a constant current must flow through them to build the necessary voltage drop for the evaluation. For this, the module CI511-ETHCAT provides a constant current source which is multiplexed over the max. 4 analog input channels.

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

Connection of resistance thermometers in 2-wire configuration

Pt100	-50 °C…+400 °C	2-wire configuration, 1 channel used
Pt1000	-50 °C…+400 °C	2-wire configuration, 1 channel used
Ni1000	-50 °C…+150 °C	2-wire configuration, 1 channel used

The measuring ranges are described in the section Measuring Ranges CI511-ETHCAT CI511-ETHCAT.

The module CI511-ETHCAT performs a linearization of the resistance characteristic.

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