Siemens S7-1200 - Page 926

Technical specifications
A.9 Thermocouple and RTD signal modules (SMs)
S7-1200 Programmable controller
926 System Manual, 03/2014, A5E02486680-AG
Technical data
SM 1231 AI 4 x RTD x 16 bit
SM 1231 AI 8 x RTD x16 bit
Cable length (meters)
100 meters to sensor max.
100 meters to sensor max.
Wire resistance
20 Ω, 2.7 Ω for 10 Ω RTD max.
20 Ω, 2.7 Ω for 10 Ω RTD max.
Table A- 174 Diagnostics
Technical data
SM 1231 AI 4 x RTD x 16 bit
SM 1231 AI 8 x RTD x16 bit
Overflow/underflow
1,2
Yes
Yes
Wire break
3
Yes
Yes
24 VDC low voltage
1
Yes
Yes
1
The overflow, underflow and low voltage diagnostic alarm information will be reported in the analog data values even if
the alarms are disabled in the module configuration.
2
For resistance ranges underflow detection is never enabled.
3
When wire break alarm is disabled and an open wire condition exists in the sensor wiring, the module may report
random values.
The SM 1231 RTD analog signal module measures the value of resistance connected to the
module inputs. The measurement type can be selected as either "Resistor" or "Thermal
resistor".
● "Resistor": The nominal range full scale value will be decimal 27648.
● "Thermal resistor": The value will be reported in degrees multiplied by ten (for example,
25.3 degrees will be reported as decimal 253). The climatic range values will be reported
in degrees multiplied by one hundred (for example, 25.34 degrees will be reported as
decimal 2534).
The SM 1231 RTD module supports measurements with 2-wire, 3-wire and 4-wire
connections to the sensor resistor.