Hall principle:
The so-called Hall effect refers to the physical phenomenon that when a magnetic field acts on carriers in current-carrying metal conductors and semiconductors, a lateral potential difference is generated. When the current passes through the Hall element, if a magnetic field is applied in the direction perpendicular to the current, a lateral potential difference (called Hall voltage) will be generated on both sides of the Hall element. Due to the change of magnetic field, the Hall element sends out pulse signals and sends them to the controller for processing, thus realizing the functions of sensors or switches such as speed measurement and position measurement.
Therefore, it is necessary to change the magnetic field to have a corresponding Hall pulse signal output. You use a round magnet to fix it on the motor shaft. If the surrounding magnetic fields are the same, there will be no output change, so you should choose a small magnet with high magnetism (such as a cuboid or a flat body) and fix it on the motor shaft, with the N pole or the S pole perpendicular to the motor shaft. Because you use a unipolar Hall, you use one pole of the magnet to point to the positive induction area of Hall, so when the magnet on the motor shaft turns to Hall's position, Hall will output a pulse signal because of the change of the magnetic field, cutting the magnetic field lines.
All Hall will change with the change of temperature, and the Gaussian values of BOP and BRP of Hall will be elegant in different degrees (commonly known as temperature drift), but according to your description, it is estimated that you are used to measure position (phase sensor) or speed (speed sensor). Then your temperature environment should not be too high, just choose the lobby at -40 to 85 degrees, and the price is relatively cheap. If the temperature exceeds 85 degrees, use Hall products with a temperature of -40 to 150, and the price will be much more expensive.