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 equipped with a toothed wheel or a gear with ferromagnetic material. It operates on the principle of detecting changes in the magnetic field caused by the moving ferromagnetic target.
Here's how it works:
Target Object: The object whose speed needs to be measured is fitted with a toothed wheel or a gear made of ferromagnetic material (e.g., iron or steel). As this target object rotates, the teeth or notches on the wheel pass by the magnetic speed sensor.
Magnetic Sensor: The magnetic sensor is a simple device that consists of a coil and a permanent magnet. The coil is wound around a core, and the permanent magnet is placed inside the core. The magnetic sensor is positioned close to the path of the rotating target object.
Magnetic Field Change: As the ferromagnetic teeth on the rotating wheel pass by the magnetic sensor, they cause fluctuations in the magnetic field in the vicinity of the sensor.
Induced Voltage: The changing magnetic field induces a voltage in the coil of the magnetic sensor due to Faraday's law of electromagnetic induction. The induced voltage is proportional to the rate of change of the magnetic field, which is directly related to the speed at which the target object is rotating.
Signal Processing: The induced voltage from the magnetic sensor is processed and converted into an electrical signal. This signal typically takes the form of electrical pulses with a frequency directly proportional to the rotational speed of the target object. The signal is then passed to the electronic control unit (ECU) or the instrument cluster of the vehicle or system.
Speed Measurement: The ECU or instrument cluster interprets the frequency of the electrical pulses to determine the rotational speed of the target object. It can then use this speed information for various purposes, such as controlling engine timing in a vehicle or displaying the speed on a dashboard.
Overall, the basic magnetic speed sensor is a straightforward and reliable way to measure rotational speed. It is commonly used in automotive applications, industrial machinery, and other systems where accurate speed information is crucial. The simplicity and durability of magnetic speed sensors make them a popular choice in various industries.