Basic principles of digital magnetic sensors

A digital magnetic sensor is a device in which the up and down states between output switches are influenced by the presence of an external magnetic field. This type of device, based on the Hall effect, is widely used in proximity, positioning, velocity, and current detection sensors. Unlike mechanical switches, they are a durable solution because they have no mechanical wear and can work even in particularly critical environmental conditions. Digital magnetic sensors are becoming increasingly widespread, especially in the automotive and consumer electronics sectors, due to their characteristics such as non-contact operation, lack of maintenance, robustness, and immunity to vibration, dust, and liquids.

Regardless of the specific application type, the basic requirement for the correct operation of the sensor is that the magnetic flux lines are always perpendicular to the sensor surface and have the correct polarity. There are many applications of digital magnetic sensors, including automotive, consumer electronics, electronic medical systems, telecommunications, and industrial process control. The position sensor is used to detect the sliding motion between the magnet and the sensor, with the two components placed at a short distance. The relative motion between the magnet and the sensor generates a positive magnetic field when the sensor moves south, and a negative magnetic field when the sensor moves north.

There are several techniques that can be used to determine position: for example, if an application requires limited and discrete positions, simple switches can be used, while for applications that require higher accuracy, linear devices can be combined with microprocessors. Location or proximity sensors can also be used to monitor the level of liquids, applied to household appliances such as washing machines or dishwashers. In this case, several Hall switches are used in combination with magnets placed on the float.

When the float rises into the tube, it will activate the corresponding discrete switch located outside the shell, providing a digital indication of the water level. Another important application involves brushless DC motors, whose speed control is electrical rather than mechanical commutation. In this regard, three digital magnetic sensors are positioned on the motor stator, while permanent magnets are placed on the rotor shaft. The automotive industry has become a leader in the global magnetic field sensor market, accounting for over 40% of the market share. The increasing demand for integrating multiple safety features into automobiles has created an opportunity for Hall sensors to be utilized in several safety related applications, such as electronic stability control systems (ESC) and anti lock braking systems (ABS).