Siemens Simatic S7-1500 - Properties; Properties of the CPU Part

Wiring
Analog Input Module AI 8xU/R/RTD/TC HF (6ES7531-7PF00-0AB0)
Manual, 09/2016, A5E36647959-AB
21
Connection: 2, 3 and 4-wire connection of resistance-type transmitters or resistance thermometers
(RTD)
The example in the following figure shows the pin assignment for 2, 3 and 4-wire
connections of resistance-type transmitters or resistance thermometers.
①
4-wire connection CHx Channel or 9 x channel status
(green/red)
②
3-wire connection
RUN
Status display LED (green)
③
2-wire connection
ERROR
Error display LED (red)
④
Analog-to-Digital Converter (ADC)
PWR
LED for power supply (green)
⑤
Electrical isolation
⑥
Backplane bus interface
⑦
Supply voltage via power supply element
⑧
Equipotential bonding cable (optional)
Figure 3-3 Block diagram and terminal assignment for 2, 3, and 4-wire connection