Magneto-resistive films: an application to hybrid non contact transducers of mechanical displacements

Transducers of mechanical displacements are emploied in large scale in electronic controls of any kind of mobile equipments and are very important for market sectors like Automotive, Aerospace, Robotic etc. Generally they are made with a sliding contact (cursor) on a Thin, Thick or Polymer conductive/resistive Film. carefully shaped for continuous conversion of longitudinal or rotational displacements into electric signals. Weakness for those transducers reside in the long therm reliability of the sliding contact on the film, especially when used in severe environmental conditions. Devices very sensitive to the Magnetic Field strength, based on Magneto-resistive films on Hall-effect are now available and used to manufacture reliable non-contact digital mechanical Transducers. The magnetic field generated by a current-carrying planar conductive film has been measured using a commercial Magnetoresistive device to control correspondence between theoretical anticipations and experimental results. Shaped "ad hoc" by photolithography the current-carrying film is able to deliver to the magnetoresistive sensor a signal proportional to its relative mechanical displacement along the film . This property of conductive film has been used to realize Hybrid non-contact analog Transducers of Angular displacements. Theory, experimental data and essential characteristics of the Transducer are presented.