Siemens Simatic S7-400 - Manual (Page 267)

Analog Modules
5-51
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Four-Conductor Connection of a Resistance Thermometer
The voltage generated at the resistance thermometer is measured via the M
+
and
M
–
terminals. When you connect, watch out for the polarity of the connected cable
(connect I
C +
and M+ as well as I
C –
and M– to the resistance thermometer).
Make sure that the connected cables I
C
+ and M+ and SO and SE+ and cables
I
C
– and M– and AGND and SE– are connected directly on the resistance
thermometer.
I
C
M
+
M
–
I
C+
I
C–
SE+
SE–
SO
AGND
Figure 5-14 Four-Conductor Connection of Resistance Thermometers on an AI