Siemens SIMATIC S7-200 - Selecting Open Wire Check; Selecting Temperature Scale

S7-200 Specifications
A-70
S7-200 Programmable Controller System Manual
A5E00066097-02
Selecting open wire check Open wire detection is performed by injecting a
25 µA current onto the input terminals. The open wire enable switch enables or
disables the current source. The open wire range check is always performed, even
when the current source is disabled. The EM 231 Thermocouple module detects
open wire if the input signal exceeds approximately 200mV. When an open wire
is detected, the module reading is set to the value selected by the sensor burnout
direction. Enable or disable the open wire current source by setting DIP switch 6
for the desired function as shown in Table A-24.
Table A-24 Selecting Open Wire Check
Open Wire
SW6
Enable open wire current 0
Disable open wire current 1
Note
• The open wire current source may interfere with signals from some low level
sources such as Thermocouple simulators.
• Input voltages exceeding approximately 200mV will trigger open wire
detection even when the open wire current source is disabled.
Selecting temperature scale The EM 231 Thermocouple module can report
temperatures in Celsius or Fahrenheit. The Celsius to Fahrenheit conversion is
performed inside the module. Use DIP switch 7 to select the temperature scale as
shown in Table A-25.
Table A-25 Selecting Temperature Scale
Scale
SW7
Celsius (C) 0
Fahrenheit (F) 1