PLC capability in handling analog and digital computing power

The mid-1980s to the 1990s, is the fastest growing PLC period, the annual growth rate has been maintained at 30 to 40 percent. During this period, PLC capability in handling analog and digital computing power,plc IO module man-machine interface capabilities and network  industrial plc  capabilities have been greatly improved, PLC gradually entering the field of process control, in some applications in the field of process control to replace the dominant DCS systems.
PLC has the versatility, plc temperature control module  ease of use, wide adaptation, can be * high anti-jamming capability, programming and simple. PLC in the industrial automation and control especially in order to control the position, in the foreseeable future, can not be replaced.　

plc as general industrial control computer

PLC as general industrial control computer, industrial and mining-oriented industrial equipment. It is easy interface, output module plc the programming language is easy for engineering and technical personnel to accept. Ladder language graphic symbol and expression and relay circuit is very close, with only a small pulse input module plc  switch on the PLC logic control instructions can easily achieve the function relay circuit. Is not familiar with the electronic circuits, computers do not understand the principles and assembly language people use computers in industrial control Plc high speed counting modules  to open the door. System design, construction workload is small, easy to maintain, easy to transform PLC logic instead of using store-wired logic, greatly reducing the external control equipment wiring, the control system design and construction period is much shorter, but also becomes easier to maintain. More important is to change the program of the same device has been possible to change the production process. It is suitable for many varieties, small batch production applications.

CPU mainly by the operator, controller

CPU mainly by the operator, controller, register and data connections between them, control and status bus constituted, plc cpu modules CPU unit also includes a peripheral chip bus interface and related circuitry. The main memory used to store programs and data, communication modules plc  is an indispensable component PLC unit.
In the user view,input module plc unnecessarily detailed analysis of the internal circuitry of the CPU, but each part is working mechanism should be enough to understand.

PLC is operated electronic digital computing device specifically

PLC is operated electronic digital computing device specifically for applications in industrial environments and design. It uses a memory can be programmed and used in the instruction execution logic  plc soe module  of its internal memory, sequential operation, timing,input module plc high speed counter plc and arithmetic operations, plc module high speed user-oriented instruction counter plc and arithmetic operations, etc., and various types through digital or analog input / output control of machinery or production processes. programmable logic controller and related peripherals, are easy and industrial control systems together into a whole, to expand the principles of the design of its functions.

Input sampling stage

In the input sampling stage, PLC scan mode sequentially reads all input states and data, and store them in the I / O image area corresponding the unit. After the end of the input plc analog input module sample, into the user program execution and output refresh period. In both stages, and even if the input data changes state, status, and data I / O of the image area of the corresponding cell is not changed. Therefore, if the input is a pulse signal, the width of the pulse signal

plc analog input output io module

must be greater than one scanning cycle, in order to ensure that in any case, the input can be read.

Output Wiring

Programmable controller with relay output, thyristor output, transistor output three kinds of forms. The output wiring into separate output and common output. When the PLC output relay or programmable logic controller plc thyristor action, the two outputs of the same number of turns. In different groups, and the voltage level can be different types of output voltage. However, the output in the same group only of the same type, the same level of power supply voltage. Since the output Plc high speed counting modules element of the PLC is encapsulated in a printed circuit board and connected to the terminal board, the load connected to the output element shorted If the burning of printed circuit board, therefore, the application of the fuse to protect the output element.

I / O modules

PLC interface with the electrical circuit, the input and output section by the (I / O) completion. I / O modules with integrated PLC's I / O circuit, the input signal status register reflects the input and output points to reflect the state of the output latch. The programmable logic controller input module signals into the electrical signals into digital PLC system, the opposite output module. I / O into the digital input (DI), digital output (DO), analog input (AI), analog output (AO) and other modules. Switch means that only the opening and closing (or 1 and 0) signals, analog two states refers to continuous change. Commonly used I / O classified as follows: Switch: Press voltage level points with 220VAC, 110VAC, 24VDC, by isolating way points, with relay isolation and transistor isolation. Analog: divided by signal type, there is a current type (4-20mA, 0-20mA), voltage type (0-10V, 0-5V, -10-10V), etc., according to the accuracy of points, there are 12bit, 14bit, 16bit, etc. . In addition to the general Plc analog input output module purpose IO, there are special IO modules, such as thermal resistance, thermocouple, pulse and other modules. Press the I / O module specifications and determine the number of points, I / O modules can be more or less, but its maximum number of CPU capacity can be managed by the basic configuration, namely by the largest floor or rack slot limit.