Connection of Resistance Thermometers in 2-wire Configuration to the \ Analog Inputs

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 CI521-MODTCP 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 to the analog input AI0. Proceed with the analog inputs AI1 to AI3 in the same way.

Connection of resistance thermometers in 2-wire configuration to the analog inputs

The following measuring ranges can be configured CI521-MODTCP and CI521-MODTCP:

Pt100	-50 °C…+70 °C	2-wire configuration, 1 channel used
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 function of the LEDs is described under Diagnosis and displays / Displays CI521-MODTCP.

The module CI521-MODTCP performs a linearization of the resistance characteristic.

To avoid error messages from unused analog input channels, configure them as “unused”.