The NPN and PNP types in laser displacement sensors mainly refer to the electrical characteristics of the sensor output signal, and the specific differences are as follows:
1. Output signal polarity:
-NPN output: The output of an NPN sensor is grounded. When the sensor detects a target object, the internal switch closes, connects the signal pin to ground (LOW), and outputs a low level. When there is no target object, the output maintains a high impedance state.
-PNP output: The output of a PNP sensor is connected to a positive power supply. When the sensor detects a target object, the internal switch closes, connecting the signal pin to the power supply (HIGH) and outputting a high level. When there is no target object, the output maintains a high impedance state.
2. Connection method:
-NPN type connection: When using NPN type sensors, the load of the sensor (such as a relay or PLC input) is usually connected to a positive power supply, and the output of the sensor is connected to the input of the load. When the sensor detects an object, the load is grounded, thereby controlling the operation of the circuit.
-PNP type connection: When using PNP type sensors, the load of the sensor is usually connected to ground, and the output of the sensor is connected to the input of the load. When the sensor detects an object, the output signal will be pulled high to power the load.
3. Application areas:
-NPN and PNP sensors can be selected according to different applications and circuit requirements. NPN type is usually used in systems that require low-level signals (or ground triggering), while PNP type is more commonly used in systems that require high-level signal triggering.
Summary: The main difference between NPN and PNP laser displacement sensors lies in their output signal polarity and connection method. The selection should be based on specific circuit and application requirements.
