Long range magnetic field measurement with magnetic sensors

Magnetic systems provide powerful tools for contact free motion detection. Such systems are very robust, being capable of operating in harsh environments, e.g. in the presence of dirt and at high temperature, and have life-times of up to decades. Another advantage is that quasi-static applications, typical for the detection of mechanical motion, enable the measurement of magnetic fields from outside of a closed system, as the magnetic fields easily penetrate solid non-magnetic materials. On the other hand, the fast decay of the magnetic field of a magnet is a known characteristic and normally a limiting factor regarding distance between magnet and sensor. To overcome this issue, a device constructed of a highly permeable material is proposed, aiming to focus the magnetic field at a sensing point, hence named “field focuser”. Similar concepts of magnetic field focusers have been proposed and are available in various geometrical designs [1, 2, 3]. Currently, there are several realizations of magnet-magnetic sensor systems where the motion of the magnet is detected by the change in field amplitude at the sensor. These systems include linear motion detection, axis rotation detection, complex composed motion detection and many others, which lead to a large range of industrial applications, especially in the automotive branch [4, 5]. This work aims to extend the knowledge on magnetic systems and help developers to understand limits and advantages of such setups.