Most magnetic sensor systems consist of a magnetic field sensor that measures the magnetic field in one or more directions and a magnetic element that creates the magnetic field. Different kind of stimulus changes the distance or the orientation of the magnetic element with respect to the magnetic field sensor or even the magnetic properties of the material in the magnetic element can change for a specific stimuli which can be detected by the sensor. Thus, with a magnetic sensor system it is possible to detect all kinds of parameters for instance distance, orientation or even different kind of molecules in a liquid. In other cases a magnetic field sensor can detect the magnetic orientation in the magnetic element (which can be used to store data as zeros and ones) positioned on a hard disk in a computer or in other types of information carrier media. The magnetic field sensor can either be a sensitive and low noise ordinary magnetoresistive sensor or a giant magnetoresistance (GMR) sensor, a Hall sensor (to be used in a wider field range) or just a coil wounded with copper windings (to be used at higher frequencies since its sensitivity increases linearly with the frequency).
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Motion and position detection | | The classic magnetic sensor system for position and orientation detection is constructed as follows. Around a permanent magnet of, for instance an NdFeB alloy (which is the strongest permanent magnet that it is possible to purchase today), there lies a magnetic field. The strength and direction of this magnetic field depends on the distance and direction to the permanent (and also on the dimension and geometry of the magnet) in a complex way. However, for small changes in direction and orientation the strength is more or less linear to the changes in both distance or changes in orientation. Together with a sufficiently sensitive magnetic field sensor (that can measure the magnetic field strength in one or more orthogonal directions) it can be used to measure changes in position down to a few micrometers up to several millimeters and angle changes down to a few milliradians up to a full rotation of an object. This kind of sensor system can be designed for many application areas where measurement changes in distance or orientation between two or more objects is required. The complete sensor system is highly cost effective in many applications. It can also be used in harsh environments (for instance in high temperature conditions). Recently it was reported that Adidas had used a magnetic detection technique in their newly developed sport shoes in order to first measure the compression of the sole of the shoe allowing the shoe to thereafter automatically adjust the damping in the sole. Using sensitive magnetic sensor systems it is also possible to detect the approach, speed and even identification of objects manufactured with magnetic materials, for instance vehicles. |