A basic inductive proximity sensor is a type of non-contact sensor used to detect the presence or absence of metallic objects within its sensing range. It operates on the principle of electromagnetic induction. Here's a step-by-step explanation of how it works:
Sensor Coil: The proximity sensor contains an inductive coil that is typically made of a wire wound around a ferrite core. This coil is connected to an oscillator circuit.
Oscillator Circuit: The oscillator circuit generates a high-frequency alternating current (AC) signal that flows through the coil. The frequency of the signal is typically in the range of tens to hundreds of kilohertz.
Metal Target Interaction: When a metal object enters the sensing range of the proximity sensor, it interacts with the magnetic field produced by the coil and the oscillator circuit.
Eddy Currents: Due to the interaction with the alternating magnetic field, eddy currents are induced within the metal object. Eddy currents are circular currents that flow within the metal material and oppose the change in the magnetic field.
Damping Effect: The presence of the metal object and the resulting eddy currents have a damping effect on the magnetic field of the sensor coil. As a result, the amplitude and phase of the oscillating current in the coil change.
Detection: The proximity sensor's electronics detect these changes in the coil's oscillation and trigger a response. Typically, the sensor monitors the amplitude or frequency of the oscillator signal to determine the presence of a metal object.
Output: Depending on the sensor's design, it can provide various types of output signals, such as a digital on/off signal (switching output) or an analog voltage/current signal proportional to the distance from the sensor to the metal object.
Detection Range: The detection range of the inductive proximity sensor depends on the size and composition of the metal object and the sensor's design. Larger metal objects and higher sensor sensitivity usually result in longer detection ranges.
It's important to note that inductive proximity sensors are specifically designed for metal object detection and may not work reliably with non-metallic objects. They are commonly used in industrial applications for tasks such as object detection, position sensing, and automation control due to their robustness and non-contact operation.