Principles of analog value processing
4.6 Wiring and connecting thermocouples
S7-300 Module data
252 Manual, 06/2017, A5E00105505-AJ
Options of compensating for the reference junction temperature
Table 4- 1 Options of compensating for the reference junction temperature
No compensation To record only the temperature difference between the measuring
point and reference junction.
Internal compensation
(for wiring and connecting, see
Connecting thermo-
couples with internal compensation box to electri-
cally isolated analog inputs
)
The internal compensation is based on a comparison using the in-
ternal temperature (thermocouple internal comparison) of the mod-
ule.
External compensation with compensation box in
the feed lines of each thermocouple (the wiring and
connecting is shown in the diagram
Wiring and
connecting of thermocouples with compensation
box to electrically isolated analog inputs
and
Wiring
and connecting of thermocouples with reference
junction (order no. M72166-xxx00) to electrically
You have already measured and compensated for the reference
junction temperature (thermocouple external comparison) using an
interconnected compensating box in the feed lines of each thermo-
couple.
Further signal processing is not required at the module.
Only for SM 331; AI 8 x TC:
External compensation with resistance thermometer
for recording the reference junction temperature
You can measure the reference temperature using a (platinum or
nickel) resistance th
ermometer, and compute it in the module for any
thermocouple.
See also
Wiring and connecting thermocouples with internal compensation (Page 253)
Wiring and connecting thermocouples with external compensation (Page 254)
Wiring and connecting transducers to analog inputs (Page 239)
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