A Hall effect pickup, or hall effect sensor, is a transducer that responds to a magnetic field. Hall sensors can sense proximity, positioning, speed and current as they detect the presence of a magnetic field and produce an output voltage.
Hall effect pickups are commonly used to detect the presence of magnetic objects in switches, pistons or valves. In this capacity, hall sensors are placed at one or both ends of a device to determine the position of the magnet and help identify when a switch is open or closed, or act as the switch themselves.
Hall sensors are also used to detect the speed and position of the rotor in a brushless DC motor. Providing position and speed information, pickups assist with DC motor control, speed regulation, and braking systems.