Siemens SIMATIC ET 200AL, System Manual

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Connecting transducers
4.7 Wiring thermocouples
Analog value processing
76
Function Manual, 06/2014, A5E03461439-AC
4.7 Wiring thermocouples
Introduction
Thermocouples are generally supplied ready-to-use. Protective casing prevents the
thermocouples from being destroyed by mechanical force, for example.
Compensating lines
The compensating lines belonging to the respective thermocouples are identified by a
special color code, because only the compensating line that is made of the material
matching the thermocouple may be used. The standardized compensating lines are
specified in DIN EN 60584. Observe the maximum temperatures in the manufacturer's
specifications.
Thermocouple connection options
There are various different ways to wire thermocouples to an analog input module:
●
Directly
①
.
● Using compensating lines
②
.
● With a compensating line to the reference junction, connected with a supply line, e.g.
copper
③
.
①
Thermocouple without compensating line
②
Thermocouple with compensating line
③
Thermocouple with compensating line and supply line
④
Compensating line (same material as thermocouple)
⑤
External reference junction
⑥
Copper supply cable, for example
Figure 4-10 Example: Wiring thermocouples to an analog input module
Further information
Further information, such as the selection of thermocouples and how they operate, can be
found in the section Thermocouples (Page 77).