![]() According to the wiring diagram of proximity sensor, we should first find out the load in the PLC. ![]() We will take FX3U PLC and S7-200 PLC as examples to explain how is the NPN proximity sensor and PNP proximity sensor connected to PLC. ![]() In other words, signal of the NPN proximity sensor flows from the load to the proximity sensor, while that of the PNP proximity sensor flows from the proximity sensor to the load. NPN proximity sensor belongs to the low level conduction and PNP proximity sensor belongs to the high level conduction. The difference of NPN proximity sensor and PNP proximity sensor lies in the conduction situation. Generally, people in the United States and Japan usually use NPN proximity sensor, while in the Europe use the PNP proximity sensor. And they can be further divided into NPN type and PNP type. And in DC circuit, the proximity sensors used include 2-wire proximity sensor, 3-wire proximity sensor and 4-wire proximity sensor. In PLC control system, we mostly use DC proximity sensors.
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