A basic inductive speed sensor, also known as an inductive proximity sensor or an inductive proximity switch, detects the speed of rotating equipment using electromagnetic principles. These sensors are commonly used in industrial applications for measuring rotational speed or counting revolutions of rotating machinery. Here's how they work:
Inductive Principle: The sensor works based on the principle of electromagnetic induction. When a conductive metal target, such as a gear or shaft, rotates in close proximity to the sensor, it induces eddy currents in the target material.
Eddy Currents: As the metal target rotates, the magnetic field of the sensor continuously changes in strength and direction. This changing magnetic field induces circulating electrical currents, known as eddy currents, in the metal target.
Changes in Eddy Currents: The eddy currents create their own magnetic fields, which interact with the sensor's magnetic field. These interactions cause changes in the inductance of the sensor's coil.
Detecting Changes in Inductance: The inductive sensor contains a coil that is connected to an electronic circuit. The circuit monitors the inductance of the coil continuously.
Frequency Output: As the target rotates and the eddy currents induce changes in the sensor's inductance, the electronic circuit processes these changes. The circuit then generates a frequency output signal that is proportional to the speed of the rotating target.
Signal Interpretation: The frequency output signal is typically fed into a controller or a digital interface that interprets the signal to calculate the rotational speed or count the number of revolutions per unit of time.
Target Material and Distance: The performance of the inductive speed sensor depends on the material and size of the rotating target as well as the distance between the sensor and the target. The sensor's datasheet usually provides information about the suitable target material, distance range, and other operational specifications.
Inductive speed sensors are widely used in applications where non-contact measurement of rotational speed is required, such as in industrial machinery, automotive systems, conveyor belts, and more. They are often chosen for their durability, simplicity, and reliability in harsh environments. However, they may have limitations in high-speed applications or when dealing with non-metallic targets, as the effectiveness of the eddy current induction depends on the material properties.