Siemens SIMATIC ET 200AL System Manual page 1454

Connecting thermocouples and thermal resistors
Connect the thermocouples, for example, to the module inputs using supply lines for
temperature compensation with dynamic reference temperature. In this case, the
temperature is acquired at the reference junction by means of a thermal resistor (RTD). This
reference junction temperature determined in this way is transferred to the analog module
with thermocouple via data records with the WRREC instruction.
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②
③
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Figure 5-14
Analog value processing
Function Manual, 06/2014, A5E03461439-AC
Thermocouple
Compensating line (same material as thermocouple)
Copper supply cable, for example
Thermal resistor (RTD)
Reference junction
Example: Connecting thermocouples/thermal resistors for compensation by means of
dynamic reference temperature
5.3 Compensation for the reference junction temperature
Thermocouples
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