Siemens Simatic S7-300 - Page 185

Priniples of analog value processing
4.5 Wiring resistance thermometers and resistors
S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04
4-11
3-wire connection of a resistance thermometer
When terminating 3-wire cables at modules equipped with four terminals, you should
generally bridge M-
and I
C
-. Always wire the connected
C
+ and M+ cables directly to the
resistance thermometer.
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Figure 4-10 3-wire connection of resistance thermometers to an electrically isolated analog input
2-wire connection of a resistance thermometer
For 2-wire connections, bridge the M
+
and I
C+
, and the M- and I
C
- terminals of the module.
The line resistance is measured at the same time.
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Figure 4-11 2-wire connection of resistance thermometers to an electrically isolated analog input