Outline the method used to actuate inductive and capacitive proximity sensors.
The correct answer and explanation is :
Inductive and capacitive proximity sensors are both types of non-contact sensors used to detect the presence or absence of objects. They operate based on different principles—electromagnetic induction for inductive sensors and electrostatic fields for capacitive sensors.
Method of Actuation for Inductive Proximity Sensors:
Inductive proximity sensors operate using electromagnetic induction. They consist of an oscillator, a coil, and an electronic circuit. When an object with a conductive material (usually metal) enters the sensor’s electromagnetic field, the object disrupts the oscillations of the coil. This disruption leads to a change in the amplitude or frequency of the oscillation, which is detected by the sensor’s electronics. The sensor then triggers an output signal, indicating the presence of the metal object.
The sensor has a coil of wire, which generates an alternating electromagnetic field. When a conductive object (like a metal) comes within range, it generates eddy currents in the object, which counteract the field and cause the oscillation of the coil to decrease or stop. This change is detected by the sensor’s electronic circuit, and the sensor responds by activating an output signal.
Method of Actuation for Capacitive Proximity Sensors:
Capacitive proximity sensors work by detecting changes in the capacitance between the sensor and the target object. A capacitor is created between the sensor’s electrode and the target (which can be any material, including metals, plastics, liquids, or even human skin). When an object approaches the sensor, the capacitance changes due to the variation in dielectric properties, as the object alters the electric field in the area.
The sensor typically has a pair of electrodes that generate an electric field. As an object approaches, it either increases or decreases the amount of charge stored in the electric field, thereby altering the capacitance. The sensor’s electronic circuit detects this change and sends an output signal in response.
Conclusion:
In summary, inductive proximity sensors detect metal objects via changes in electromagnetic fields, while capacitive proximity sensors detect a wide range of materials by sensing changes in capacitance. Both sensors are used in automation systems where non-contact detection is required.