Due to the increase of the AC input current limiting circuit, isolation and rectification of the three links, therefore, the delay time of the input signal than the DC input circuit is longer, it is plc programmable controller shortcomings. However, due to the high voltage input terminal, so the reliability of the input signal is higher than the DC input circuit. General, plc cpu AC input methods for oil mist, dust and other high-speed counter modules environments, the response of the less demanding situations, while the DC input mode is better for the environment, electromagnetic interference is not punished, for situations that require high responsiveness .
