Faults and alarms

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Faults and alarms



Malfunctions and alarms should support operating and maintenance personnel in troubleshooting, point out critical conditions and help to avoid faulty conditions. It must be possible to clearly distinguish between malfunction and operating messages.


In addition to a central summary message, alarms and faults must be displayed according to the following criteria:

» Activation of protective and monitoring devices (e.g. circuit breaker, thermal contact).

» Exceeding or falling below limit values of physical quantities (current, pressure, temperature, filling level, etc.)

» Monitoring of control sequences according to time and sequence

» Internal monitoring of devices and systems (PLC, servos)

» Activation of safety devices for personal protection



For the visualisation of faults and alarms, we prefer alphanumeric text displays. For control systems with a small scope, an optical individual display using indicator lamps is sufficient. Function displays of aggregates (e.g. hydraulic motor, skin drives) should flash together with the sum fault message in case of faults. The signalling of critical alarms should be supported by alarm sounders or flashing lights.


Malfunction and diagnosis

- Faults are to be displayed in plain text in the respective national language, if possible with a diagnostic display and note.


Basic information on error handling

- All movements and programme sequence steps must be equipped with an error recognition

which facilitates the localisation of the occurring error.


- Programme sequence errors, bus errors, hardware errors, etc. must be processed via corresponding modules in the programme and displayed. If a fault is detected, it must be guaranteed that danger to man and machine is averted.

and the machine is averted.


- Fault messages must not be volatile; it must not be possible to reset the fault until it has been acknowledged. Acknowledgement must not be possible until the cause of the malfunction has been eliminated.


- The fault messages must be meaningfully grouped in separate data modules for further processing by higher-level systems. The fault detection must be effective in the automatic and semi-automatic (manual) operating modes.