There are various classification methods for PLC (Programmable Logic Controller), which can be classified according to different standards. Here are some common PLC classification methods:
Classified by structural form:

Integrated PLC: The power supply, CPU, I/O interface and other components are all centralized in one chassis, with a compact structure, small size, and low price, suitable for small PLC applications.

Modular PLC: Each component of the PLC is made into several separate modules, such as CPU module, I/O module, power module, etc., with flexible configuration, easy expansion and maintenance, suitable for medium and large PLCs.

Classified by function:

Low end PLC: It has basic functions such as logic operation, timing, counting, shifting, self diagnosis, monitoring, etc. It may also have a small amount of analog input/output, arithmetic operation, data transmission and comparison, and communication functions. It is mainly used for single machine control systems with logic control, sequential control, or a small amount of analog control.

Mid range PLC: In addition to the functions of a low-end PLC, it also has strong analog input/output, arithmetic operations, data transmission and comparison, number system conversion, remote I/O, subroutines, and communication networking functions, making it suitable for complex control systems.

High end PLC: In addition to the functions of a mid-range PLC, it also adds signed arithmetic operations, matrix operations, bit logic operations, square root operations, and other special function operations, table making, and table transfer functions. High end PLCs have stronger communication networking capabilities and can be used for large-scale process control or to form distributed network control systems, thereby achieving factory automation.

Classified by I/O points:

Small PLC: The number of I/O points is less than 256, with a single CPU (8-bit or 16 bit) and a user program storage capacity of less than 4KB, mainly controlled by switch values.

Medium sized PLC: with 2562048 I/O points, using dual or multiple CPUs, and a user program memory capacity of 28KB or larger PLC.

Large PLCs: PLCs with more than 2048 I/O points, dual or multiple CPUs (16 bit or 32-bit), and user program memory capacity of 8-16KB or larger