Siemens Simatic S7-400 - Manual (Page 305)

Analog Modules
5-89
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Wire Break Check for Temperature or Resistance Measurement
The wire break check is intended primarily for temperature measurements (TC,
RTD) or resistance measurements. Always parameterize the wire break check in
these cases as this ensures that, in the event of a wire break, the measured value
provided by the module accepts the data for overrun 7FFFH.
Special Characteristics of the Wire Break Check for the Voltage Measurement
Methods
In some transmitters, incorrect measured values may be obtained due to the fact
that the wire break check is enabled. If so, disable the wire break check.
The reason Some transmitters try to correct the test current and in doing so corrupt
the setpoint value provided.