How to differentiate between PNP and NPN sensors using a multimeter
PNP type sensors and NPN type sensors work by utilizing the two states of saturation and cutoff of the triode, so they are both switching sensors. The commonly used ones are PNP type proximity switch and NPN type proximity switch. PNP-type sensors are high-level output sensors, while NPN-type sensors are low-level output sensors. Therefore, you need to pay attention to the actual wiring of the two sensors. This type of switching sensor generally has three lead-out lines, namely the power supply VCC, 0V line, and output signal line.
It is actually very simple to distinguish between these two types of sensors with a multimeter. The signal output line is connected to the power supply VCC and the PNP sensor is working. The signal output line is connected to the 0V line and the NPN sensor is working.
For example, if it is a switching sensor with 24VDC power supply, send 24VDC power to the PNP or NPN sensor, and set the multimeter to the DC voltage range. You can determine whether it is a PNP sensor or an NPN sensor, and you can also determine whether it is a normally open or normally closed sensor.
Don't give them a trigger signal first. Use a multimeter to connect one test lead to the signal output line and the other test lead to the VCC line and 0V line respectively. If there is a 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 and measure it in the same way as a multimeter. There is a 24VDC voltage between the measured output signal line and VCC. This switch-type sensor is an NPN normally open sensor. There is a 24VDC voltage between the measured output signal line and the 0V line. This sensor is a PNP normally open sensor. It is quite easy to determine what type of switch type sensor they belong to. As long as you have a multimeter, you can solve many doubts.
