Siemens SIMATIC S7-400 Reference Manual page 213

3-conductor connection of a resistance thermometer
With a 3-conductor connection to modules with 4 terminals per resistance thermometer, you
must set up a jumper between M- and I
The module compensates in this circuit for the effect of the line resistance between the module
and the resistance thermometer/resistor.
Make sure that the connected cables I
the resistance thermometer.
To get an accurate measurement, make sure that the connected cables M+, I
SE+, SO and AGND are the same length and have the same cross-section.
Figure 5-13
I
C+
I
C-
M
+
M
-
2-conductor connection of a resistance thermometer
For 2-conductor connections, bridge the M
Note: Cable resistance is also measured.
Figure 5-14
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
M+
SE+
M-
SE-
I
SO
C+
I AGND
C-
I
C
3-conductor connection of a resistance thermometer to an electrically isolated analog input
Constant current line (positive)
Constant current line (negative)
Measuring line (positive)
Measuring line (negative)
M+
M-
I
C+
I
C-
2-conductor connection of a resistance thermometer to an electrically isolated analog input
5.12 Connecting resistance thermometers and resistors
- and SE- and AGND (see Figure).
C
+ and M+ and SO and SE+ are directly connected to
C
and I , and the M
+ C+
Analog modules
+ and I
C
and I terminals of the module.
- C-
- and
C
213