Huber, T. (2010). Wireless strain-sensor based on magnetoacoustic resonance [Diploma Thesis, Technische Universität Wien]. reposiTUm. http://hdl.handle.net/20.500.12708/160252
This thesis deals with the development of a new type of sensor.<br />The underlying principle of the new type of sensor bases on the combination of magnetostriction and magnetoacoustic resonance. The sensor-technology is suitable for measuring pressure, temperature, flow velocity, liquid viscosity, magnetic field and mass loading.<br />All these possible applications have only been tested in laboratories and never found their way to a final commercial product. The only widespread use is in electronic article surveillance.<br />Magnetostriction can be observed in almost any material, especially in a wide range of metal-alloys containing Cobalt, Nickel and Iron. The physical properties of these materials strongly depend not only on their composition but also on the chosen heat-treatment, the magnetic-history or both combined. One objective of this thesis was to find materials with a high change of Young's module when changing the external magnetic-field, the so called delta-E-effect.<br />The change of the external magnetic field can be produced either by changing the distance to the field producing magnet(s) or by changing the magnetization of materials near the sensor.\\ The focus of the thesis relies on the above mentioned change of the magnetization if stress or pressure is applied to a magnetostrictive material. This can be used as a stress-sensor.<br />Such a strain sensor, constructed of a transducer and a resonator both based on amorphous softmagnetic materials, as manufactured by "Metglas Inc." or "Vacuumschmelze GmbH & Co KG", was built. This sensor shows a almost linear change of resonance frequency within a strain range of +-0.1 mm/m. For the proposed sensor the so called gauge factor G is defined as the relative change of the resonance frequency divided by the strain epsilon = delta-l/l, G = (delta-f/f)/(epsilon).<br />Our proposed wireless sensor optained G = 325 which is significantly higher than the gauge factor of standard metal foil strain gauges which is in the range between 2 and 5.<br />