Hall Generator

an element that operates on the basis of the Hall effect and is used as a measuring transducer in automation, electronics, and measurement technology. A Hall generator is a thin rectangular plate (with an area of several square millimeters) or film of semiconductor material, such as Si, Ge, InSb, or InAs, and has four electrodes for current input and the output of a Hall electromotive force (emf). To avoid mechanical damage, the plate is mounted, or the film is deposited in vacuum, on a sturdy substrate of dielectric material, for example, mica or a ceramic. To obtain the greatest effect, the plate or film is made as thin as possible.

Hall generators are used for contactless measurements of magnetic fields in the range from 10^–6 to 10⁵ oersteds. To measure weak magnetic fields, the generator is inserted in a gap in a ferromagnetic or ferrite core; this technique makes it possible to increase substantially the sensitivity of the generator. In a semiconductor, the concentration of charge carriers, and hence the Hall coefficient, may be temperature dependent. Therefore, precision measurements require either the maintenance of a constant temperature or the use of heavily doped semiconductors; the latter measure reduces the sensitivity of the generator.

A Hall generator may be used to measure any physical quantity that is linearly related to the strength of a magnetic field. In particular, current intensity can be measured, because a measurable magnetic field is produced around a current-carrying conductor. Ammeters based on Hall generators have been developed for the measurement of currents of up to 100 kiloamperes.

Hall generators are employed in multipliers in analog computers. In this case, two currents that are proportional to the quantities to be multiplied are used, one to power the generator and the other to produce the magnetic field. The Hall emf is proportional to the product of the two currents.

Hall generators are also used in instruments that measure linear or angular displacements, magnetic-field gradients, magnetic flux densities, or the output of electric motors, as well as in contactless inverters and in playback heads of sound-recording systems.