Board mount Hall effect / magnetic sensors are components designed to detect the presence of a magnetic field, typically in the form of a switch or output signal. The sensors are generally located on a board mounted to a surface, similar to a printed circuit board, and monitor changes in magnetic fields to detect the presence of magnetic objects, such as a ferrous wheel, rotor, or engine shaft. An important application for these sensors is for automotive and industrial applications, where the magnetic field generated by a rotating part can be used to measure the angular rotation of that part. They can also be used to detect the presence of other metallic objects such as coins, screws, or nuts. The signal from the magnetic or hall effect sensors can be used to trigger a switch or other electrical device, or to provide an output proportional to the strength of the magnetic field.