(1) Number of input and output points: According to the number of input and output points supported by PLC, it can be divided into small PLC, medium PLC and large PLC. Generally speaking, small PLCs have fewer input and output points and are suitable for simple control tasks; while large PLCs have more input and output points and are suitable for complex control tasks.

(2) Functional modules: According to the different functional modules supported by PLC, it can be divided into basic PLC and advanced PLC and other levels. Basic PLC usually only has the most basic input and output control functions, while advanced PLC has more functional modules, such as analog input and output, communication interface, motion control, etc.

(3) Performance parameters: According to the performance parameters of PLC, it can be divided into low-end PLC, mid-end PLC and high-end PLC and other levels. Low-end PLCs usually have low processing speed and storage capacity and are suitable for simple control tasks; while high-end PLCs have higher processing speed and storage capacity and are suitable for complex control tasks.

(4) Application field: According to the application field of PLC, it can be divided into industrial PLC and non-industrial PLC and other levels. Industrial PLC usually has high anti-interference ability and reliability, and is suitable for the field of industrial automation control; non-industrial PLC is mainly used in commercial, household and other fields.