A 3-wire Autonics Proximity Sensor is used to detect the presence of an object without physical contact and send a clean signal to a controller such as a PLC. It has three wires — power (V+), ground (0V), and output. This separate output line allows better stability, faster switching, and accurate response compared to a 2-wire sensor, which combines power and signal in the same line. The 3-wire configuration ensures consistent operation and reduced electrical noise in automation systems.
In an inductive sensor, the circuit produces a high-frequency electromagnetic field at the sensing face. When a metal object enters this field, the oscillation weakens, and the detection circuit identifies the change, switching the output signal. In capacitive sensors, the sensor detects changes in capacitance when materials like plastic, glass, or liquid approach the sensing area.
When a target object is detected, the sensor’s output (PNP or NPN) changes state, sending a clear ON/OFF signal to the control system. The 3-wire design delivers high accuracy, quick response, and strong noise immunity, making it ideal for precise detection in modern industrial automation and machinery control applications.
A 3-wire proximity sensor works by detecting the presence of an object without physical contact and sending a clean electrical signal to a controller such as a PLC. These sensors have three wires — one for power supply (V+), one for ground (0V), and one for output signal. The third wire provides a separate path for the output, ensuring better signal stability and faster switching compared to 2-wire sensors.
In an inductive proximity sensor, an internal oscillator circuit generates a high-frequency electromagnetic field at the sensing face. When a metal object enters this field, it creates eddy currents that weaken the oscillation. The sensor’s detection circuit senses this change and switches the output signal. The output (either PNP or NPN) changes state, sending an ON or OFF signal to the PLC, depending on the target’s presence.
In a capacitive proximity sensor, the sensing face forms one plate of a capacitor, while the surrounding environment acts as the other. When a non-metallic object like plastic, wood, or liquid enters the field, the capacitance changes. The internal circuit detects this change and triggers the output, just like in inductive types. The sensor’s output remains stable and fast because power, ground, and signal lines are separated.
In simple terms, a 3-wire proximity sensor detects objects by sensing changes in an electromagnetic (inductive) or electrostatic (capacitive) field. When it detects a target, the sensor’s output wire sends a clear ON/OFF signal to the control system. This design gives excellent response time, higher accuracy, and better noise immunity — making 3-wire proximity sensors the standard choice for modern industrial automation systems.