ISTVIBH2BCC
ISTVIBH2BCC
ISTVIBH2BCC
emphasized that the programmable controller is qualitatively different from the drum and mechanical sequential controller described in the past. Due to the introduction of a new generation of electronic devices such as microprocessor and semiconductor memory, PLC and the specified instructions for programming, can be modified flexibly, that is to use software to achieve the purpose of “programmable” 
1. Analog instrument control system: analog instrument control system dominated in the 1960s and 1970s. Its significant disadvantage is that the analog signal has low accuracy and is susceptible to interference.
2. Centralized digital control system: Centralized digital control system dominated in the 1970s and 1980s. The MCU, PLC, SLC or microcomputer are used as the controller, and the digital signal is transmitted inside the controller, so it overcomes the defects of low accuracy of analog signal in the analog instrument control system, and improves the anti-interference ability of the system. The advantage of the centralized digital control
system is that it is easy to calculate and judge the control according to the global situation, and the choice of the control mode and the control machine can be unified scheduling and arrangement. The shortage is that the controller itself is very demanding, must have enough processing power and extremely high reliability, when the system task increases, the
