A basic magnetic speed sensor, also known as a magnetic speed pickup or magnetic speed encoder, is a device used to measure the speed of a rotating object. It works on the principle of magnetic induction and typically consists of two main components: a magnet and a magnetic sensor.
Here's how it operates:
Magnet: The rotating object, whose speed you want to measure, is fitted with a small permanent magnet. This magnet is mounted in such a way that it rotates in sync with the object's motion. For example, in a vehicle's speed sensor, the magnet could be attached to a rotating wheel or shaft.
Magnetic Sensor: The magnetic sensor is a Hall effect sensor, a type of transducer that can detect changes in magnetic fields. It is positioned close to the path of the rotating magnet. When the magnet rotates, it generates a changing magnetic field, which the Hall effect sensor can detect.
Hall Effect: The Hall effect is a phenomenon in which an electric current is generated perpendicular to both an applied magnetic field and the direction of the current flow. When the rotating magnet passes by the magnetic sensor, it creates a changing magnetic field. This changing magnetic field induces a small voltage in the Hall effect sensor.
Signal Processing: The voltage induced in the Hall effect sensor is extremely small, so it needs to be amplified and processed to produce a usable speed signal. The sensor's output is conditioned by an analog signal conditioner or an application-specific integrated circuit (ASIC) to provide a digital or analog signal proportional to the rotational speed.
Speed Output: The processed output signal from the magnetic speed sensor can be used in various ways, depending on the application. For example, in an automotive context, the signal may be fed to the vehicle's engine control unit (ECU) to calculate vehicle speed, monitor wheel rotations, or control transmission shifts.
In summary, a basic magnetic speed sensor uses the Hall effect to detect changes in a magnetic field generated by a rotating magnet. By processing the output signal, it provides a useful measurement of the rotational speed of the object to which it is attached. These sensors are widely used in various applications, including automotive speedometers, industrial equipment, and many other systems that require speed measurement or monitoring.