The analog input module is configured to output module plc precautions when

First, we must get to know what is the "two-wire current signal" input, what is the "four-wire current signal" input. Simply put: When the sensor comes with power supply, transport a 0 ~ 20mA or 4 ~ 20mA current loop signal through two current signal line out without PLC via analog interfaces to  plc temperature control module provide 24VDC power supply module, the We call it "four-wire current signal." At this point, output module plc should the current loop input analog signal on the channel configuration is 4DU (4 ~ 20mA), the analog input module configured to span the card position [C] when the sensor itself, without power supply, you need to PLC analog input module to provide external power supply 24VDC when we called "two-wire current signal." Under the "two-wire current signal" configuration, analog input module current and voltage signals are shared two lines. In this case, the plc modular  current loop input analog signal on the channel configuration is 2DU (4 ~ 20mA), the analog input module configured to span the card position [D], as shown above: The above two configurations, the actual do not be mistaken in!
If configuration errors, such as the "active" four-wire current input signal is mistakenly configured as "passive" two-wire current input signal, the analog signal input interface PLC will withstand external 24VDC input current signal is brought power supply, which can easily lead to plc logic controller  burnout PLC analog input module! ! ! In practical applications, to be careful, pay attention to the difference between them