Inductive Proximity Sensor

Inductive sensor is an electronic proximity sensor which detects metallic objects without touching them. When the detecting distance is 5mm or less 1 inch and your application calls for metal sensing, the inductive proximity (IP) sensor provides the needed solution.

Working Principal of Inductive Proximity sensor

Inductive proximity sensors operate under the electrical principle of inductance. Inductance is the phenomenon where a fluctuating current, which by definition has a magnetic component, induces an electromotive force (emf) in a target object. In circuit design, one measures this inductance in H (henrys). To amplify a device’s inductance effect, the sensor twists wire into a tight coil and runs a current through it

An inductive proximity sensor has

four elements:

1:Coil

2:Oscillator

3:Trigger circuit

4: An output.

The oscillator is an inductive capacitive tuned circuit that creates a radio frequency. The electromagnetic field produced by the oscillator is emitted from the coil away from the face of the sensor. The circuit has just enough feedback from the field to keep the oscillator going. When a metal target enters the field, eddy currents circulate within the target. This causes a load on the sensor, decreasing the amplitude of the electromagnetic field. As the target approaches the sensor, the eddy currents increases, increasing the load on the oscillator and further decreasing the amplitude of the field. The trigger circuit monitors the oscillator’s amplitude and at a predetermined level switches the output state of the sensor from its normal condition (on or off). As the target moves away from the sensor, the oscillator’s amplitude increases. At a predetermined level the trigger switches the output state of the sensor back to its normal condition (on or off).

Interfacing with Arduino:

/ digital pin 2 has a PNP sensor attached to it. int metalSensor = 2; // the setup routine runs once when you press reset: void setup() { // initialize serial communication at 9600 bits per second: Serial.begin(9600); // make the sensor's pin an input: pinMode(metalSensor, INPUT); }// the loop routine runs over and over again forever: void loop() { // read the input pin: int sensorState = digitalRead(metalSensor); // print out the state of the sensor: Serial.println(sensorState); delay(1000); // delay in between reads for stability}

Code:

/ digital pin 2 has a PNP sensor attached to it.

int metalSensor = 2;

// the setup routine runs once when you press reset:

void setup()

{

// initialize serial communication at 9600 bits per second:

Serial.begin(9600);

// make the sensor’s pin an input:

pinMode(metalSensor, INPUT);

}// the loop routine runs over and over again forever:

void loop(){

// read the input pin:

int sensorState = digitalRead(metalSensor);

// print out the state of the sensor:

Serial.println(sensorState);

delay(1000);

// delay in between reads for stability}

 

Advantages:

  1. They are very accurate to other technologies.
  2.  Have high switching rate.
  3.  Can work in harsh environment condition.

Disadvantages:

  1. It can detect only metallic target.
  2. Operating range may be limited

 

Reference:

https://www.instructables.com/id/3-Wire-Inductive-Sensor-and-LeoStick/

https://how2electronics.com/inductive-capacitive-proximity-sensor/#Proximity_sensors

http://www.ijste.org/articles/IJSTEV2I9108.pdf

https://forum.arduino.cc/index.php?topic=520398.15

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