A basic magnetic speed sensor, also known as a magnetic pickup or magnetic sensor, is a device used to measure the rotational speed of a target object. It operates on the principle of electromagnetic induction. Here's how it works:
Principle of Electromagnetic Induction: When a conductor (such as a wire) moves through a magnetic field or when there is a change in the magnetic field around a conductor, an electric voltage is induced in the conductor. This phenomenon is known as electromagnetic induction.
Target Object: The speed sensor typically consists of a permanent magnet and a coil of wire. The target object, whose speed needs to be measured, is equipped with a metal toothed gear, a ferromagnetic gear, or a similar metal structure that can disrupt the magnetic field.
Permanent Magnet: The magnetic sensor is placed near the target object in such a way that the permanent magnet creates a magnetic field around the coil.
Fluctuating Magnetic Field: As the target object rotates or moves, the teeth or metal structure on it disturb the magnetic field around the coil. This movement creates fluctuations in the magnetic field strength near the coil.
Induced Voltage: The fluctuations in the magnetic field induce voltage in the coil of wire, following the principle of electromagnetic induction. The voltage's frequency and amplitude are directly related to the speed at which the target object is rotating or moving.
Signal Processing: The induced voltage signal is then processed by electronic circuitry, which typically includes amplification and conditioning circuits. These circuits help strengthen and shape the voltage signal, making it suitable for further processing and analysis.
Speed Calculation: By analyzing the frequency of the induced voltage signal, the speed sensor can calculate the rotational speed or velocity of the target object. The frequency of the signal is proportional to the rotational speed of the target object.
Output: The processed speed information is usually provided as an electrical output, which can be in the form of analog voltage, current, or digital pulses. This output can then be connected to other systems, such as engine control units (ECUs) in vehicles or industrial control systems, for various applications.
Magnetic speed sensors are widely used in various industries for measuring the speed of rotating machinery, such as engines, turbines, pumps, and conveyor belts. They are simple, reliable, and cost-effective devices for speed measurement and control.