Magnetic Position Measurement: From Amplitude to Direction

摘要

Magnetic field sensors based on the Hall effect are nowadays probably the most widely used magnetic sensors. More than 2 billion Hall sensors were sold worldwide in 2001. There is hardly any new car in the world without a dozen of Hall sensors inside. Most of currently applied Hall magnetic sensors are low-cost discrete devices. However, an increasing part of them comes in the form of integrated CMOS circuits. Interestingly, they are relatively rarely used to measure just a magnetic field. Much more, Hall sensors are applied as key components in contact-less sensors for linear position, angular position, velocity, rotation, and current. Magnetic field sensors are increasingly replacing more conventional angle sensors such as switches, potentiometers, optical encoders and current sensors. The main reason to switch to magnetic sensors is the fact that they are compact, reliable, wear free, insensitive to pollution and dust, and inexpensive. Conventional magnetic position sensors work after the principle that a magnet or ferromagnetic structure either slides by or rotates close to a magnetic sensor (Fig. 1). The motion changes the magnetic field component along the sensitive axis of the sensor and the output voltage of the sensor changes correspondingly.