User Manual

Technical specifications
A.8 RTD and Thermocouple modules
Easy Book
Manual, 03/2014, A5E02486774-AF
317
Table A- 46 Analog output representation for current (CPU 1215C and CPU 1217C)
System
Current output range
Decimal
Hexadecimal
0 mA to 20 mA
32767
7FFF
See note 1
Overflow
32512
7F00
See note 1
32511
7EFF
23.52 mA
Overshoot range
27649
6C01
27648
6C00
20 mA
Rated range
20736
5100
15 mA
34
22
12 mV
0
0
0 mA
Negative values Negative values are not
supported
1
In an overflow condition, analog outputs will behave according to the device configuration properties settings. In the
"Reaction to CPU STOP" parameter, select either: "Use substitute value" or "Keep last value".
A.8
RTD and Thermocouple modules
The thermocouple (TC) modules (SB 1231 TC and SM 1231 TC) measure the value of
voltage connected to the analog inputs. This value can be either temperature from a TC or
volts.
● If voltage, the nominal range full scale value will be decimal 27648.
● If temperature, the value will be reported in degrees multiplied by ten (for example, 25.3
degrees will be reported as decimal 253).
The RTD modules (SB 1231 RTD and SM 1231 RTD) measure the value of resistance
connected to the analog inputs. This value can be either temperature or resistance.
● If resistance, the nominal range full scale value will be decimal 27648.
● If temperature, the value will be reported in degrees multiplied by ten (for example, 25.3
degrees will be reported as decimal 253).
The RTD modules support measurements with 2-wire, 3-wire and 4-wire connections to the
sensor resistor.
Note
The RTD and TC modules report 32767 on any activated channel with no sensor connected.
If open wire detection is also enabled, the module flashes the appropriate red LEDs.
Best accuracy will be achieved for th
e 10 Ω RTD ranges if 4 wire connections are used.
The resistance of the connection wires in 2 wire mode will cause an error in the sensor
reading, and therefore accuracy is not guaranteed.