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 gear. It is commonly used in various applications, such as automotive, industrial machinery, and speed monitoring systems. The operation of a basic magnetic speed sensor involves the following components and steps:
Sensor Housing: The sensor is usually housed in a protective casing made of non-magnetic material. This housing shields the sensor from external influences and provides mechanical stability.
Permanent Magnet: Inside the sensor housing, there is a small permanent magnet. The magnetic field of this magnet is used to sense the presence of ferromagnetic teeth on the rotating target.
Ferromagnetic Target: The object whose rotational speed is to be measured has a toothed wheel or gear made of ferromagnetic material. These teeth are evenly spaced around the circumference of the wheel or gear.
Coil or Hall Effect Sensor: A coil or a Hall Effect sensor is placed close to the permanent magnet inside the housing. Both these types of sensors can detect changes in magnetic fields.
Magnetic Field Variation: As the ferromagnetic teeth pass near the sensor, they disturb the magnetic field of the permanent magnet. The presence of a tooth causes a localized change in the magnetic field strength at the position of the coil or Hall Effect sensor.
Induced Voltage (for Coil Sensor): In a coil sensor, the changing magnetic field induces a voltage across the coil according to Faraday's law of electromagnetic induction. The voltage signal produced by the coil corresponds to the passing teeth and their frequency is directly proportional to the rotational speed of the target.
Hall Effect Output (for Hall Effect Sensor): In a Hall Effect sensor, the magnetic field variation causes a change in the output voltage of the sensor. The Hall Effect sensor generates a voltage output that varies with the magnetic field strength, and this output is directly related to the rotational speed of the target.
Signal Conditioning: The raw output from the magnetic sensor might require some signal conditioning, such as amplification and noise filtering, to ensure accurate and reliable speed measurements.
Speed Calculation: The conditioned output is then processed by electronic circuits to calculate the rotational speed of the target object. This information can be displayed on a dashboard or used for control and monitoring purposes in various systems.
In summary, a basic magnetic speed sensor operates by detecting changes in the magnetic field caused by the passing ferromagnetic teeth of a rotating target. The sensor output is processed to determine the rotational speed of the target object.