How to distinguish between PNP and NPN sensors with a multimeter
PNP-type sensors and NPN-type sensors use the saturation and cut-off states of the triode to work, so they all belong to the switching value sensor. Commonly used are PNP type proximity switches and NPN type proximity switches. PNP-type sensors are high-level output sensors, while NPN-type sensors are low-level output sensors. Therefore, it is necessary to pay attention to the actual wiring of the two sensors. This type of switch sensor generally has three lead wires, which are the power supply VCC, 0V line, and output signal line.
It is actually very simple to distinguish these two sensors with a multimeter. The signal output line is connected to the power supply VCC and works as a PNP sensor, and the signal output line is connected to the 0V line to work as an NPN sensor.
For example, a switch sensor with 24VDC power supply, send 24VDC power to the PNP or NPN sensor, and turn the multimeter to the gear of DC voltage. It can be judged whether it is a PNP type sensor or an NPN type sensor, and it can also be judged whether it is a normally open type or a normally closed type switch type sensor.
Don’t give them a trigger signal first, connect one pen of the multimeter to the signal output line without moving, and connect the other pen to the VCC line and the 0V line respectively. If there is 24VDC voltage between the output signal line and the VCC power line, it can be judged that the switch sensor is an NPN normally closed sensor. If there is a 24VDC voltage between the output signal line and the 0V line, it is a PNP normally closed sensor.
Give it a trigger signal, the same as the multimeter measurement method. There is a 24VDC voltage between the measurement output signal line and VCC. This switch sensor is an NPN normally open sensor. There is a 24VDC voltage between the measurement output signal line and the 0V line. This sensor is a PNP normally open sensor. It is quite easy to judge what type of switch sensors they belong to. As long as you have a multimeter, you can solve many doubts.
