ABB AC500 PLC - Connection of Resistance Thermometers in 2-wire Configuration; Connection of Resistance Thermometers in 3-wire Configuration

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 I/O module
provides a constant current source which is multiplexed over the 8 analog channels.
UP
ZP
1.0
I0-
1.1
I1-
1.8
UP
1.9
ZP
PTC
2.0
I0+
2.1
I1+
2.8
UP
2.9
ZP
Pt100
Pt1000
Ni1000
Fig. 60: Connection example
Pt100 -50 °C...+70 °C 2-wire configuration, one
channel used
Pt100 -50 °C...+400 °C 2-wire configuration, one
channel used
Pt1000 -50 °C...+400 °C 2-wire configuration, one
channel used
Ni1000 -50 °C...+150 °C 2-wire configuration, one
channel used
The I/O module 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".
Connection of Resistance Thermometers in 3-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 I/O module
provides a constant current source which is multiplexed over the max. 8 (depending on the con-
figuration) analog channels.
Device Specifications
I/O Modules > Analog I/O Modules
2019/04/173ADR010121, 13, en_US524