plc IO module operating principles and classification

PLC interface with the electrical circuit, the input and output section by the (I / O) completion. plc IO module integrates the PLC's plc IO module circuit, the input signal status register reflects the input and output points to reflect the state of the output latch. The input module signals into the electrical signals into digital PLC system, the opposite output module. plc IO module into digital input (DI), digital output (DO), analog input (AI), analog output (AO) and other modules. Commonly used plc IO module 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 purpose IO, there are special IO modules, such as thermal resistance, thermocouple, pulse and other modules.