Terminology » Other Wireless » PNP vs NPN Sensor: Understanding the Key Differences

PNP vs NPN Sensor: Understanding the Key Differences

pnp sensor npn sensor sensor automation sinking

This article clarifies the differences between PNP and NPN sensors, two common types of sensors used in various automation and control systems. We’ll explore how they work and examine their respective 3-wire diagrams.

PNP Sensor

  • This type of sensor sources its positive power to the output, meaning it provides the positive voltage when activated. Therefore, it’s often called a “Sourcing sensor.”

  • The following image (Figure 1) illustrates a typical 3-wire diagram for a PNP sensor.

PNP Sensor 3 wire diagram Alt text: PNP Sensor 3 wire diagram

  • The “Load” in the diagram represents the device that the sensor powers. This could be anything from a lamp or relay to a pneumatic valve or Programmable Logic Controller (PLC) input. Essentially, it’s what the sensor is switching ON or OFF.

NPN Sensor

  • In contrast to the PNP sensor, the NPN sensor sinks its ground to the output. This means it provides a path to ground when activated. Consequently, it’s known as a “sinking sensor”.

  • Figure 2, shown below, illustrates a typical 3-wire diagram of an NPN sensor.

NPN Sensor 3 wire diagram Alt text: NPN Sensor 3 wire diagram