Measuring small variations in weak magnetic fields can prove rather difficult at times, especially when other stronger magnetic fields are present. Take for example the magnetic sensors used in the automotive industry. They are used to measure a whole range of parameters, including temperature variations, minute air currents or small magnetic fields. The position of the seats and the mirror, for example, are also tracked and adjusted with the help of magnetic sensors.

A small permanent magnet attached either to the seat or the mirror generates a magnetic field that varies when moved in relation to the magnetic sensor. This variation is stored by the on-board computer and later used to modify the positions of both accordingly. Very innovative, one may say, although the cables running besides the magnetic sensor, such as those used by heating elements, or the stepper electric motors also generate magnetic fields when powered, thus interfering with the correct operation of the sensor. One solution would be to magnetically screen such devices from the rest of the car, but the process is not at all easy, not to mention that it is very expensive.

The alternative comes from the Fraunhofer Institute for Integrated Circuits IIS whose researchers developed a magnetic sensor that is able to detect small variations in weak magnetic fields and requires no magnetic screening against more powerful fields. It is in fact composed of a series of sensors placed on a chip that can measure all the components of a magnetic field at once and determine how its position changes.

"This sensor enables us for the first time to identify magnetic interference fields as such and to separate them from the useful field. The sensor works perfectly even when the interference field is considerably larger than the useful field. There is therefore no need for shielding", says Dr. Hans-Peter Hohe, IIS team leader.

Aside from requiring no magnetic screening, the newly developed sensor is also able to function in temperatures up to 150 degrees Celsius and can be mass produced since it is based on standard CMOS techniques.