Analog signal is the most basic process signal (pressure, temperature, flow, etc.) input form in the automated process control system. The process signals in the system pass through the transmitter, convert these detection signals into unified voltage and current signals, and transmit these signals to the controller (PLC) in real time.
PLC converts these analog signals into internal numerical signals through calculation and conversion. So as to realize the monitoring and control of the system.
It can be seen from the signal input process of PLC analog quantity that in the automatic process control system, the input of analog quantity signal is very complicated. However, in the current industrial site, the processing of analog signals has basically adopted the current signal transmission method. Compared with the voltage signal method, the current signal has stronger anti-interference ability, longer transmission distance and stable signal.