„Innovative sensor system for a contactless measurement of torsional moment, angular velocity and analysis of structural integrity of ferromagnetic shafts in the heavy industry“
General description of the technology (current stage):
The measurement of torsional stress is mainly accomplished by the use of strain gauges under the utilization of different technological concepts (electrical chance of resistive probes or change of diffraction in optical waveguides). For all these concepts it is necessary to allow a physical contact to the measuring object. For all these concepts a non-negligible effort has to be spent in order to realize the data transfer between the sensor and the evaluation electronics (telemetry). The application under special service conditions (elevated temperatures, presence of aggressive lubricants or abrasive particles) impede a proper operation or require frequently system maintenance.
The developed concept of the sensor operates completely contactless and is therefore applicable for rotating or static shafts. The sensor concept offers the potential to be miniaturized and is therefore applicable outside (shaft) or inside the measuring object (hollow shaft).
The principle of the multifunctional sensor can be described by the function of a split transformer consisting of an E-shaped magnetic flux guide carrying an emitter coil surrounded by two identical receiver coils. The emitter coil is fed by an alternating current providing a weak measuring field and a weak magnetization of the measuring object. The application of an alternating current enables the possibility in order to measure changes in the amplitude or phase distribution of the measuring field. The measurable phase shift between the torsional moment influenced receiver signals behaves proportionally to the effective torsional moment in the shaft. The angular velocity of the shaft is determined by the rotation speed dependent induction signals.