In order to adapt to the use in the industrial environment, compared with the general control device, the PLC machine has the following characteristics:
High reliability and strong anti-interference ability
The reliability requirements of industrial production for control equipment:
Long mean time between failures
Fault repair time (average repair time) is short
There are usually two kinds of failures caused by any electronic equipment:
Occasional failure. Faults caused by external harsh environments such as electromagnetic interference, ultra-high temperature, ultra-low temperature, over-voltage, under-voltage, vibration, etc. This kind of failure, as long as it does not cause damage to the system components, once the environmental conditions return to normal, the system will also return to normal. But for PLC, after being affected by the outside world, the information stored inside may be destroyed.
Permanent failure. Failure due to irrecoverable destruction of components.
If the conditions for the occurrence of occasional faults can be limited, if the PLC can be unaffected in harsh environments or the consequences of the impact can be limited to a minimum, so that the PLC can automatically return to normal after the harsh conditions disappear, so that the mean interval between failures can be improved. Time; if some diagnostic measures and appropriate protection measures can be added to the PLC, when a permanent fault occurs, the fault point can be quickly found and the fault can be limited to local areas, which can reduce the average repair time of the PLC. To this end, various PLC manufacturers have taken a variety of measures in terms of hardware and software, so that PLC not only has strong self-diagnosis ability, can give error information in time, stop running and wait for repair, but also make PLC have a very strong self-diagnosis ability. Strong anti-interference ability.
