Identification of photoelectric switch NPN and PNP

The photoelectric switch can be divided into two states: NPN output and PNP output. When there is a current flowing out of the sensor (PNP output type), the current flows from the power supply through the output of the sensor to the load, and then to the ground. When the photoelectric switch with current flow (NPN output type) is turned on, the current flows from the power supply through the load to the output end of the photoelectric switch, then flows to the ground, and finally flows into the ground of the system. PNP and NPN photoelectric switches generally have three lead wires, + pole, signal output, and-pole. NPN means that when there is a signal trigger, the signal output line is connected to the ground, which is equivalent to output low level. PNP means that when there is a signal trigger, the signal output line is connected to the positive pole, which is equivalent to a power line that outputs a high level. Three-wire PNP and NPN photoelectric switches generally have three lead wires, which are + pole,-pole, and output out signal output line. NPN means that when a signal is triggered, the signal output line is connected to the ground, which is equivalent to outputting a low level. PNP means that when a signal is triggered, the photoelectric switch signal line output is connected to the positive pole, which is equivalent to outputting a high-level signal.

Another measurement method is to use a multimeter with a power supply. The method is as follows: Connect the power supply to the VCC and GND terminals. The Shanghai Guangju Photoelectric Switching Power Supply is DC5-36V. Use an object on the photoelectric switch measurement terminal to make the indicator light light up. The DC voltage range of the multimeter measures the voltage between the output and the ground (the red test lead is connected to OUT and the black test lead is connected to GND). If there is a voltage, it means that the output high potential is PNP type. If there is no voltage, it means that the output low potential is an NPN type photoelectric switch.