553BTechnical specifications
A.7 Thermocouple and RTD signal modules (SMs)
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
711
The SM 1231 Thermocouple (TC) analog signal module measures the value of voltage
connected to the module inputs. The temperature measurement type can be either
"Thermocouple" or "Voltage".
● "Thermocouple": The value will be reported in degrees multiplied by ten (for example, 25.3
degrees will be reported as decimal 253).
● "Voltage": The nominal range full scale value will be decimal 27648.
Table A- 96 Wiring diagrams for the thermocouple SMs
SM 1231 AI 4 x TC 16 bit (6ES7 231-5QD30-0XB0
SM 1231 AI 8 x TC bit (6ES7 231-5QF30-0XB0)
①
TC 2, 3, 4, and 5 not shown connected for clarity.
Note
Unused analog inputs should be shorted.
The thermocouple unused channels can be deactivated. No error will occur if an unused
channel is deactivated.
A.7.1.1
Basic operation for a thermocouple
Thermocouples are formed whenever two dissimilar metals are electrically bonded to each
other. A voltage is generated that is proportional to the junction temperature. This voltage is
small; one microvolt could represent many degrees. Measuring the voltage from a
thermocouple, compensating for extra junctions, and then linearizing the result forms the
basis of temperature measurement using thermocouples.