Wire break detection (EP1839-0042)
The wire break detection is deactivated in the factory setting. You can activate it for each channel individually with the CoE parameters 80x00:01hex "Enable wire break detection".
The assignment of the CoE parameters to the connection designations can be found in the chapter Assignment of the connections.
Wire break message
When wire break detection is enabled, a wire break is reported in two ways:
- In the process data object DI Diagnosis the corresponding bit is set to TRUE.
- The status LED of the affected channel lights up red. See chapter EP1839-0042.
Functioning
The wire break detection monitors the input current of the respective digital input. If the input current falls below the threshold value of approx. 47 µA, this is interpreted as a wire break.
The box can detect a wire break even in the "off" state because the threshold value is so low that it is exceeded by the leakage current of usual sensors.
Troubleshooting
Ideally, a wire break is only reported if there is actually a wire break in the sensor cable. However, there are other reasons for reporting wire break:
- The sensor cable is short-circuited to GND.
- No sensor is connected.
- The sensor is a mechanical switch.
See section "Mechanical switches".
Mechanical switches
A mechanical switch has no significant leakage current when it is open. If you use a mechanical switch as a sensor, a wire break is reported when the switch is open.
You have two options to solve this problem:
- Deactivate the wire break detection for the affected channel.
- Connect a resistance in parallel with the mechanical switch.
The resistance must be dimensioned so that the current through the resistance exceeds the wire break detection threshold.