Hall sensors - highly sensitive, unipolar, bipolar, analogue, digital, 1st level, 2nd level
Magnetic field sensors respond to the presence or absence of a magnetic field in their surroundings depending on the type of sensor. Hall sensors are the most popular magnetic field sensors. The functionality of the sensors is based on the hall effect of the same name. Due to an adjacent magnetic field, a charging deficiency develops on one side of the live sensor and a charging surplus on the other side. A switching operation is triggered by the internal structure of the sensor depending on the design. Other magnetic field sensors respond to the magnetic field of the earth and are used for determining the position and location.
Unipolar magnetic field sensors only respond to the magnetic fields, whose field lines penetrate the sensor from a specific direction. The sensor switches only in this case. In case of bipolar hall sensors, the sensor responds to field lines from both directions. These sensors are often used as tachometers. There are highly-sensitive magnetic field sensors, which respond to the magnetic field of the earth. These sensors are generally used for location determination.
The basis of these highly-sensitive magnetic field sensors is an anisotropic, magneto-resistive technology. Four permalloy resistances (Wheatstone bridge) are the basic structure of a 1, 2 or 3-axes system. These sensors measure direction and strength of extremely small magnetic fields. The smallest measuring range of these components is ± 200 microtesla. For comparison: The magnetic field of the earth has a strength of about 60 µT.