Hall Effect Sensors

Hall effect sensors respond to magnetic fields. There are different types of sensors depending on how the output voltage is intended to behave in relation to the magnetic field.

Analog, linear: Provides a continuous output voltage that is proportional to the strength of the magnetic field. The output voltage varies linearly with the field intensity, from a low to a high value.

Digital: Provides a discrete output signal, high or low, based on the sensor’s threshold levels.

Latching (Bistable): Changes state when the magnetic field exceeds its threshold with a certain polarity, for example a north pole. The output remains in this state even if the magnetic field is removed. To switch back, a magnetic field with the opposite polarity, for example a south pole, must pass the corresponding threshold.

Unipolar: Responds to one polarity, for example a south pole. Returns to the unaffected state when the magnetic field disappears.

Omnipolar: Responds to both polarities, north and south. Returns to the unaffected state when the magnetic field disappears.

Bipolar: Requires the opposite polarity for reset.

Ratiometric: A ratiometric Hall sensor produces an analog output voltage that is proportional to both the applied magnetic field and the supply voltage. This means the sensor's output scales linearly with the supply voltage.
When the magnetic field is zero, the output voltage corresponds to half the supply voltage, i.e., 2.5 V at 5 V supply. With a positive magnetic field, the output voltage increases upward (toward 5 V), while with a negative magnetic field, it decreases downward (toward 0 V).

Magnetoresistive: (MR) sensors detect magnetic fields by measuring changes in the electrical resistance of a ferromagnetic material. They are used to achieve higher sensitivity and better resolution, especially at weak magnetic fields.

Hysteresis: Is used, for example, in thermostats and sensors to avoid rapid on–off cycling at threshold values, which stabilizes the system. In control and automation engineering, it prevents unwanted oscillations near the equilibrium point.
Without hysteresis, small variations in the magnetic field, electrical noise, or mechanical vibrations could cause the output to switch rapidly back and forth around the threshold. With hysteresis, a defined and reproducible switching behavior is obtained, which is particularly important in applications such as speed measurement, position detection, and limit switches.
The magnitude of the hysteresis is typically specified in magnetic flux density, for example in millitesla or gauss. A larger hysteresis provides higher immunity to disturbances but poorer resolution in position determination, while a smaller hysteresis provides higher sensitivity but requires a cleaner environment. The choice of hysteresis is therefore a design parameter that is adapted to the requirements of the application.