The magnetic field lines will deviate from their original direction and undergo distortion near magnetic materials such as iron, so the direction and magnetic field strength of the magnetic field lines will change with the movement of iron gears.

GH1820 contains two independent Hall sensor pairs. If one Hall sensor faces the tooth top of the gear and another Hall sensor faces the tooth valley (backlash) of the gear, a differential magnetic field signal is generated.

As the gears move from the tooth top to the tooth valley, the polarity of this differential magnetic field signal also changes at the same speed. The corresponding magnetic field change is converted into a voltage signal through an internal signal processing circuit, which triggers and controls the output stage circuit to switch between the on (output low level) and off (output high level) states.

The maximum differential magnetic field signal occurs at the edge of the teeth. When the differential magnetic field signal exceeds ∆ BOP, the output tube of GH1820 will open (conduct, VOUT is low level). It should be pointed out that there is no change in magnetic field during static state, so the output signal is uncertain.