Three classifications of programmable controller PLC

Abstract: The three classification information of programmable logic controller PLC is provided by excellent flowmeter and flowmeter production and quotation manufacturers. There are many kinds of PLC products, and their specifications and performances also vary. The classification of PLC is usually roughly classified according to the difference in its structure, the difference in function, and the number of I/O points. 1. According to the structural form, P can be classified according to the structural form of the PLC. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following are the details of three classification articles of programmable logic controller PLC. There are many kinds of PLC products, and their specifications and performances also vary. The classification of PLC is usually roughly classified according to the difference in its structure, the difference in function, and the number of I/O points. 1. Classification by structural form According to the structural form of PLC, PLC can be divided into two types: integral type and modular type. (1) Integral PLC Integral PLC integrates the power supply, CPU, I/O interface and other components in one chassis, and has the characteristics of compact structure, small size and low price. Small PLC generally adopts this kind of integral structure. Integral PLC is composed of basic unit (also called host) and expansion unit with different I/O points. In the basic unit, there are CPU, I/O interface, expansion port connected with I/O expansion unit, and interface connected with programmer or EPROM writer. There are only I/O and power supply in the expansion unit, and there is no CPU. The basic unit and extension unit are generally connected by flat cables. Integral PLC can generally be equipped with special functional units, such as analog units, position control units, etc., to expand its functions. (2) Modular PLC Modular PLC is to make each component of PLC into several separate modules, such as CPU module, I/O module, power supply module (some are included in CPU module) and various functional modules. Modular PLC consists of frame or base plate and various modules. The modules are mounted on the sockets of the frame or base plate. The characteristics of this modular PLC are flexible configuration, which can be selected according to the needs of different scale systems, and easy to assemble, easy to expand and maintain. Large and medium-sized PLCs generally adopt a modular structure. There are also some PLCs that combine the characteristics of integral and modular to form a so-called stacked PLC. The CPU, power supply, I/O interface, etc. of the stacked PLC are also independent modules, but they are connected by cables, and each module can be stacked layer by layer. In this way, not only the system can be flexibly configured, but also can be made compact. 2. Classification by function: According to the different functions of PLC, PLC can be divided into three categories: low-grade, mid-grade and high-grade. (1) Low-grade PLC has basic functions such as logic operation, timing, counting, shifting, self-diagnosis, monitoring, etc. It can also have a small amount of analog input/output, arithmetic operation, data transmission and comparison, communication and other functions. Mainly used for logic control, sequence control or a small amount of analog control single-machine control system. (2) In addition to the functions of low-end PLC, mid-range PLC also has strong analog input/output, arithmetic operation, data transmission and comparison, digital system conversion, remote I/O, subroutine, communication networking and other functions. Some can also add functions such as interrupt control and PID control, which are suitable for complex control systems. (3) In addition to the functions of mid-range machines, high-end PLCs also add signed arithmetic operations, matrix operations, bit logic operations, square root operations and other special function functions, tabulation and table transfer functions. High-end PLC machines have stronger communication and networking functions, and can be used for large-scale process control or to form a distributed network control system to realize factory automation. 3. Classification according to the number of I/O points According to the number of I/O points of the PLC, the PLC can be divided into three categories: small, medium and large. (1) Small PLCs with 256 or less I/O points are small PLCs. Among them, the number of I/O points is less than 64 points for the ultra-small or micro PLC. (2) Medium-sized PLCs with I/O points of more than 256 and less than 2048 points are medium-sized PLCs. (3) Large-scale PLCs with more than 2048 I/O points are large-scale PLCs. Among them, the number of I/O points exceeds 8192 points for the super large PLC. In practice, the strength of the general PLC function is related to the number of I/O points, that is, the stronger the function of the PLC, the more I/O points it can configure. Therefore, the small, medium and large PLCs we usually refer to are not only different in the number of I/O points, but also indicate that their corresponding functions are low-grade, mid-grade and high-grade. The above is the whole content of this article. You are welcome to inquire about the flowmeter selection and quotation of our factory. 'Three Classifications of Programmable Logic Controller PLC'

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