Siemens SIMATIC ET 200AL System Manual page 1423

Connecting transducers
4.1 Overview
Abbreviations used in the figures
Key to the abbreviations in the figures below:
AI
M
L+
M +/M
n
I +/I
Cn
U +/U
n
I +/I
n
COMP+/COMP-
I
Comp
U
V
U
CM
U
ISO
M
ANA
Lines for analog signals
Always use shielded twisted-pair cables to wire the analog signals. This improves immunity.
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Analog input module
Ground connection
Supply voltage connection
- Measuring input, channel n
n
- Current output to thermal resistor (RTD) channel n
Cn
- Voltage input channel n
n
- Current input channel n
n
Compensation input
+/I - Current output for compensation
Comp
Feed voltage at channel (the connection can be used for 2-wire
transducer (2DMU) or with ET 200eco PN and ET 200pro for 2/4-wire
transducer).
Potential difference between the reference points of the measuring
inputs / the analog ground M
Potential difference between the reference points of the measuring
inputs and the central ground
Reference point of the analog ground
ANA
Function Manual, 06/2014, A5E03461439-AC
Analog value processing