If a current-carrying conductor is located in a magnetic field, a force acts on the charge carriers perpendicular to the current and magnetic field direction. The resulting charge separation is called Hall effect and results in a measurable Hall voltage. This is proportional to the Hall coefficient and the magnetic field strength. The Hall coefficient and its sign in turn depend on the charge carrier density and the type of charge carriers.
In a doped semiconductor, either negatively charged electrons or positively charged “holes”, ie missing electrons, can be responsible for a current flow. In a conventional electrical conductor such as copper, however, only electrons flow.
The Hall coefficient can be measured if the magnetic flux density of the magnet used is known, by determining the conductor thickness, the Hall voltage and the current intensity. The effect described above allows a non-contact and precise measurement of magnetic fields. However, using a permanent magnet with known magnetic flux density, a whole range of other parameters can be determined.
This is used for example in the automotive industry, where numerous sensors z. B. for the measurement of speed, level or torque are used. Thanks to contactless measurement, Hall effect sensors are hardly susceptible to external influences and therefore wear-resistant.
Even very strong magnetic fields, such as those used in magnetic resonance imaging (MRI) can be determined by means of the Hall effect.