Answer: (1) Programming device. The programmer is an indispensable device for PLC development and application, monitoring operation, inspection and maintenance. It is used for programming, making some system settings, and monitoring the working conditions of the PLC and the system controlled by the PLC, but it does not directly participate in the field control operation. Small programmers PLC generally have handheld programmers. At present, the programmer is generally a computer (running programming software).
(2) Human-machine interface. The simplest human-machine interface is indicator lights and buttons. At present, the application of integrated operator terminals with LCD screens (or touch screens) is becoming more and more widespread, and it is very popular for computers (running configuration software) to act as human-machine interfaces.
(3) Input and output devices. Used to permanently store user data, such as EPROM, EEPROM writers, barcode readers, potentiometers for inputting analog quantities, printers, etc.
