Magnetic field Hall sensors

Magnetic field Hall sensors are the most used sensor for accurate magnetic field measurements at room or low temperature. They are based on the application of Hall effect.

Principle. When a DC electrical current I flows along a plate-shaped conductor placed in a transverse magnetic field H, a emf e appears (Fig. 1).

This is known as Hall effect and the magnitude of the Hall emf is proportional to the product of the current I and the field H. The Hall effect occurs in metals and semiconductors, but it is much larger in the latter. If the current I is kept constant the Hall voltage is proportional to the field strength H. If the current is alternating (AC) e is also alternating. The sensing element is known as Hall probe. InSb is one of the semiconducting materials historically used to construct Hall sensors. The Hall probes can be made very small.

The reproducibility of magnetic field Hall sensors is normally within 1 % over repeated thermal cycles between low and room temperature. These magnetic field sensors also show excellent linearity which is often maintained up to high magnetic field (20 Tesla about). A room temperature magnetic calibration standard is supplied. The latter allows the calibration in magnetic field at room temperature and operation in the whole temperature range.

Magnetic field Hall sensors are provided as axial or transverse probes (Fig. 2).

Transverse probes –determine the magnetic field value perpendicular to the probe plane. Axial probes - determine the magnetic field value parallel to the probe plane. Because of the small size of the probe one can measure the magnetic field strength or field gradient in a certain confined region.

The Hall sensor is fragile and must be handled carefully. It is commercially available as a bare element with connector and cable or encapsulated in a brass or fiber tube to avoid damage or breakage.

They are recommended for measuring magnetic field strength at the great majority of applications: DC low and high magnetic fields, AC and pulsed magnetic fields.