Hall probes

Devices that can be used to measure magnetic fields are called Hall probes or Hall sensors. They are based on the so-called Hall effect, which the American physicist Edwin Herbert Hall was able to prove for the first time in 1879. This discovery is considered a groundbreaking milestone in the research field of the electrical properties of metals.

What does the Hall effect mean?

The so-called Hall effect occurs when a current-carrying conductor is in a magnetic field. This creates an electrical voltage that is perpendicular to the direction of current flow and magnetic field.
This Hall voltage is calculated by the current I, the magnetic flux density, B, the thickness of the semiconductor sample d and the so-called Hall constant : :



: is a material constant and is given in cubic meters per coulomb. It is derived from the electric field strength E_y, the electrical current density j_x and the magnetic flux density:



The electrons are deflected by the Lorentz force, causing an excess of electrons on one side of the conductor and an electron deficiency on the other side. This charge separation creates an electric field (Hall voltage) that works against the Lorentz force and can even compensate it. The resulting Hall voltage changes immediately depending on changes in current and magnetic field.

The Hall effect is absolutely necessary to understand how Hall probes work.

How do Hall probes work?

When building Hall probes, one mostly uses thin, crystalline semiconductor layers that are equipped with four electrodes. Current is fed in via two opposite electrodes. The electrodes lying orthogonal to it measure the Hall voltage.

For the application of the current-carrying Hall probe, it is introduced into a magnetic field perpendicular to it. The Hall voltage that can now be measured is proportional to the magnetic field strength and the current (mobility of the charge carriers). The magnetic field can be measured based on the current strength. Conversely, the Hall probe can also measure the current. If the magnetic field is generated by a current-carrying conductor (e.g. a coil), the current strength can be determined potential-free.

What are the possible uses for Hall probes?

In addition to measuring magnetic flux density and current, Hall probes are also used in other areas, including:

  • Non-contact and contactless signal transmitters
  • Magnetic field cameras
  • Determination of layer thicknesses
  • Automotive industry (belt buckle, door locking system, gear shift, etc.)
  • Position detection of moving permanent magnets


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