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What is a Hall sensor?

　 Hall sensor is a kind of magnetic field sensor made according to Hall effect, which is widely used in industrial automation technology, detection technology and information processing. The Hall effect is a basic method to study the properties of semiconductor materials. The Hall coefficient measured by the Hall effect experiment can determine important parameters such as the conductivity type, carrier concentration and carrier mobility of semiconductor materials.

　　 Hall sensors are divided into linear Hall sensors and switching Hall sensors.

　　 1. Linear Hall sensor is composed of Hall element, linear amplifier and emitter follower, it outputs analog quantity.

　　2. The switch-type Hall sensor is composed of a voltage regulator, a Hall element, a differential amplifier, a Schmitt trigger and an output stage, and it outputs a digital quantity.

　　Hall voltage changes with the intensity of the magnetic field, 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 by the amplifier in the integrated circuit, the voltage can be amplified enough to output a strong signal. If the Hall IC is used for sensing, mechanical methods are 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 blades are 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 chip can be used as an ignition timing sensor. Hall effect sensor is a passive sensor, it needs an external power supply to work, this feature enables it to detect low-speed operation.