Magnetostrictive Bimetal Sensors

The output of project is given by a novel bending sensor based on an amorphous magnetic ribbon, a so-called magnetic glass. As a matter of fact, pure bending sensors have been unknown so far. As the basic sensor principle, the ribbon is supplemented by a nonmagnetic counter ribbon bending yielding compression of the magnetic ribbon. The resulting change of magnetic behavior yields extremely high sensitivity. For example, applying the sensor to the thorax gives a mixed signal which reflects both the cardiac activity and the respiratory activity in exact synchronism. Project aim was the establishment of a multi-parametric sensor family taking advantage of the magneto-elastic effect. All sensor versions exhibit a strongly magnetostrictive amorphous ribbon of typically 30 micrometer thickness. As a novel principle, the ribbon is combined with a nonmagnetic counter ribbon. Bending of the resulting bimetal yields strong compression of the magnetic ribbon in connection with strong changes of its magnetic behavior. The amplitude of the resulting sensor signal can be adjusted in a wide range through a variation of the counter ribbon thickness. Different versions of bimetal activation yield various sensor types comprising the following: - bending sensors - stress sensors - displacement sensors - strain sensors - sensors for circumference changes - acceleration sensors - temperature sensors Specific attractiveness of the sensor family results from the following: (a) All sensor versions use the same common element, i.e. the low-cost bimetal strip. (b) The sensitivity can be adjusted in a very simple way. (c) High durability is given through minimum wear (no electric contacts). (d) All sensor components being compact, cheap and robust which favors the competitive power of different sensor types all based on the same principle. (e) Specific sensor versions allow non-contact detection, e.g. of the temperature of a liquid in a closed tank. This offers novel aspects of applications. Possible applications are given in many fields, especially in those were high sensitivity is more relevant than high precision. Examples are automotive or domestic appliance, and - in special - appliance in biomedical engineering. At present, the sensor development is carried on within the EC-GROWTH project B-SENS which is coordinated by the project leader.