What Is a Hall Effect Sensor?

The Hall sensor is a magnetic field sensor based on the Hall effect. The Hall effect is a type of magnetoelectric effect.

Hall effect sensor, also called Hall sensor , is a

This phenomenon was discovered by Hall (AHHall, 1855-1938) in 1879 while studying the conductive mechanism of metal. Later discovered that semiconductors,

The Hall voltage changes with the change of the magnetic field strength. The stronger the magnetic field, the higher the voltage, the weaker the magnetic field, and the lower the voltage. The Hall voltage value is very small, usually only a few millivolts, but it can be amplified enough to output a strong signal by being amplified by an amplifier in an integrated circuit. If the Hall IC is used for sensing, a mechanical method is needed to change the magnetic field strength. The method shown in the figure below uses a rotating impeller as a switch to control the magnetic flux. When the impeller blade is in the air gap between the magnet and the Hall IC, the magnetic field deviates from the integrated chip and the Hall voltage disappears. In this way, the change in the output voltage of the Hall IC can indicate a certain position of the impeller drive shaft. Using this working principle, the Hall IC can be used as an ignition timing sensor. Hall-effect sensors are passive sensors, which require an external power source to work. This feature enables them to detect low-speed operation. ^[2]

Hall probes use indium compound crystals, such as indium halide. The crystal size is about 5 square millimeters. It is placed on an aluminum base and becomes a probe through packaging. The crystal plane is perpendicular to the bottom side of the probe, and the bottom side is made of non-ferromagnetic material to avoid affecting the magnetic field by itself. The leads from the crystal pass through the bottom side and enter the circuit module.

When the probe is placed in a magnetic field, when the current flows through the crystal, the carriers are deflected by the Lorentz force, which causes the carriers to be unevenly distributed on the crystal. Therefore, the Hall voltage can be detected on the aluminum base at both ends of the crystal .

Hall probe can measure weak earth magnetic field. The Hall detector first needs to be calibrated according to a known magnetic field strength. The probe then needs to be placed in the proper direction so that the geomagnetic field current lines pass directly through it. Then placed in the opposite direction, the read current density is twice the Earth's magnetic current density. ^[2]