A basic magnetic speed sensor, also known as a magnetic speed encoder or a magnetic pickup sensor, is a device used to measure the rotational speed of a moving object, typically a gear, shaft, or wheel. It operates based on the principle of detecting changes in magnetic fields caused by the motion of a magnet past a sensor element. This technology is commonly used in various applications such as automotive speedometers, industrial machinery, and robotics.
Here's how a basic magnetic speed sensor works:
Magnet and Target Wheel: The system consists of two main components – a permanent magnet and a target wheel. The permanent magnet is usually attached to the rotating part of the system (e.g., a gear or wheel), while the target wheel is typically a circular disk with evenly spaced teeth or magnetic regions.
Sensor Element: The sensor element is a stationary component placed adjacent to the path of the rotating target wheel. It contains a Hall-effect sensor or another type of magnetic sensor capable of detecting changes in the magnetic field.
Hall Effect: The Hall-effect is a physical phenomenon that occurs when a magnetic field is applied perpendicular to the flow of electric current in a conductor. When the magnetic field changes, it induces a voltage difference across the conductor, creating an electrical signal proportional to the magnetic field strength.
Detection of Changes: As the target wheel rotates, the permanent magnet attached to it generates a changing magnetic field. This changing magnetic field is detected by the sensor element. When a tooth or a magnetic region of the target wheel passes the sensor, it causes a fluctuation in the magnetic field detected by the sensor.
Signal Generation: The sensor generates electrical pulses as it detects changes in the magnetic field. These pulses correspond to the teeth or magnetic regions passing by the sensor. The frequency of these pulses is directly proportional to the rotational speed of the target wheel. This is because the more teeth or magnetic regions that pass by the sensor in a given time period, the faster the rotation.
Signal Processing: The electrical pulses generated by the sensor are typically sent to signal conditioning and processing circuits. These circuits may include amplifiers, filters, and counters to improve the quality of the signal and convert it into a digital form that can be easily processed by a microcontroller or other control systems.
Speed Calculation: The microcontroller or control system processes the digital pulse signal and calculates the rotational speed of the target wheel based on the pulse frequency. This speed information can then be used for various purposes, such as displaying the speed on a dashboard, controlling machinery, or sending data to other systems.
In summary, a basic magnetic speed sensor relies on the Hall-effect or similar magnetic sensing principles to detect changes in magnetic fields caused by the rotation of a target wheel with teeth or magnetic regions. The resulting electrical pulses are processed to determine the rotational speed of the moving object.