Why do machinery manufacturers require "PLC priority" when recruiting electricians?

PLC has spread to all walks of life, almost every enterprise is using PLC, and the maintenance of PLC control system has become the daily work of electricians. There is almost no problem with PLC itself, and the faults in the system are generally caused by sensors (such as limit switches and proximity switches) and actuators (such as contactors and solenoid valves) outside PLC. The maintenance of external faults generally only needs the external wiring diagram of PLC and the basic knowledge of PLC. In this sense, the maintenance of PLC control system is similar to that of relay control system, even simpler and more convenient. The led on the PLC module is used to indicate the on/off state of each switch input/output point, which brings great convenience to fault finding. PLC program is very useful for fault finding of complex control system. If the equipment manufacturer provides the program or does not encrypt it, you need to know the program of PLC in order to better maintain the system. If it is necessary to reform the existing system or design a new system, you should be able to read and design programs. PLC comes from relay control system. The ladder diagram program is very close to the representation of relay circuit diagram. PLC is specially designed for factory electrical personnel. If it only involves switch control but not relay control, generally only twenty or thirty basic logic instructions are needed, so it is not difficult to read, modify and design such a program. Practice has proved that. Even if the education level is not high, if you are familiar with relay circuitization, you can read and design a simple ladder diagram program of switch control system through hard work. Reading or designing complex control system programs requires understanding the basic knowledge of computers, mastering a large number of application instructions of PLC, the use of various hardware modules, network communication and analog closed-loop control and other related fields.