Development: Microprocessors emerged in the the early 1970s. It was quickly introduced into programmable controllers, which enabled PLC to increase the functions of operation, data transmission and processing, and completed the industrial control device with real computer characteristics. At this time, PLC is the product of the combination of microcomputer technology and relay conventional control concept.
After the development of the personal computer, in order to facilitate and reflect the functional characteristics of the programmable controller, the programmable controller is named programmable Logic Controller (PLC). In the late the mid 1970s, the programmable controller entered the practical development stage, the computer technology has been fully introduced into the programmable controller, so that its function has taken a leap.
Higher computing speed, ultra-small volume, more reliable industrial anti-jamming design, analog operation, PID function and extremely high cost performance have laid its position in modern industry. In the the early 1980s, programmable controllers have been widely used in advanced industrial countries. There is a growing number of countries in the world that produce programmable controllers and rising production.
This indicates that the programmable controller has entered a mature phase. From the the 1980s to the middle of the 90, PLC was the fastest growing period, the annual growth rate has been maintained at 30~40%.
In this period, PLC in the processing of analog capacity, digital computing ability, man-machine interface capabilities and network capabilities have been greatly improved, PLC gradually into the field of process control, in some applications to replace the dominant DCs system in the field of Process control. In the late 20th century, the development of programmable controller was characterized by more adaptation to the needs of modern industry. This period developed a large machine and ultra-small machine, the birth of a variety of special functional units, the production of a variety of human-machine interface units, communication units, so that the application of programmable controller industrial control equipment supporting more easily.