A basic magnetic speed sensor, also known as a magnetic pickup or magnetic encoder, is a device used to measure the rotational speed of a rotating object, such as a wheel, shaft, or gear. It operates on the principle of detecting changes in magnetic field strength as the target object rotates past the sensor.
Here's a description of the operation of a basic magnetic speed sensor:
Construction: The sensor consists of a magnet and a coil. The magnet is typically mounted on the rotating object, while the coil is fixed to a stationary surface in close proximity to the magnet.
Magnetic Field Variation: As the rotating object turns, the magnetic field around the magnet changes. This change in the magnetic field strength induces a voltage in the stationary coil due to Faraday's law of electromagnetic induction. The voltage generated in the coil is proportional to the rate of change of the magnetic field, which is directly related to the speed of the rotating object.
Signal Generation: The induced voltage in the coil is usually in the form of an electrical pulse or a sine/cosine wave, depending on the type of magnetic sensor used. The frequency of these pulses or waves is directly proportional to the rotational speed of the object being monitored.
Signal Processing: The output signal from the coil is sent to a signal processing circuit. This circuit typically converts the analog signal into a digital one, amplifies it, and shapes it for better accuracy and noise rejection.
Speed Measurement: Once the signal is processed, the speed sensor provides an output that represents the rotational speed of the target object. The output can be in various formats, such as pulses per revolution (PPR) or revolutions per minute (RPM), depending on the application and the sensor's configuration.
Application: The speed information obtained from the magnetic speed sensor is commonly used in various applications, including automotive systems (such as speedometers and anti-lock brake systems), industrial machinery control, robotics, and other applications where speed monitoring is essential.
In summary, a basic magnetic speed sensor detects changes in magnetic field strength as a rotating object passes by the sensor, and it converts these changes into an electrical signal that represents the rotational speed of the object. This simple yet effective mechanism makes magnetic speed sensors widely used in a wide range of applications.