The Helmholtz Coil describes a coil arrangement that consists of two short coils with large radius or edge length respectively. These coils are set up in parallel on the same axis. In distance of the radius / edge length a current is flowing through the coils concordantly. Its field can be characterized with a bell-shaped increase towards the coil centre. The overlay of both fields creates an area with homogenous magnetic field accessible for tests and measurement tasks.

The geometry of a Helmholtz Coil is either cylindric or quadratic. Due to its three-dimensional arrangement magnetics fields can be generated in any direction by the variation of the current ratio between both coils. The strength of the magnetic field depends on the coil current linearly and is nearly location-independent (interiorly). Given the coil geometry, current and number of windings the magnetic field strength can be calculated analyticaly along the axis. The Helmholtz Coil is an excellent device for the calibration of sensor technology, such as HALL-, magneto-resistive, Fluxgate- and SQUID-magnetometers.