engleski

Eddy-Current Displacement Transducer with Extended Linear Range and Automatic Tuning

Design details and measurement results of the eddy-current displacement transducer with extended linear range and automatic tuning are presented. The transducer is based on resonant impedance inversion method of transfer curve linearization where the displacement probe circuit is kept in resonance by the resonance control loop. The transducer exhibits extended linear range due to compensation of displacement probe losses by a negative impedance converter (NIC) at the transducer input. Particular attention is paid to the NIC design and its temperature compensation. The new voltage controlled NIC circuit is introduced which can be easily realized with a standard commercial integrated circuit (LM 1496). Details of the transducer's reference generator and the NIC control voltage generator are presented too. The transducer's linear range extends from 0.25 mm to 3.75 mm (approximately 44% of the 8 mm probe diameter) while maintaining non-linearity within ± 2% F.S. This is at least 75% improvement to the best commercially available eddy-current displacement transducers (80 mil ~2 mm linear range for 8 mm probe). Further linearization could be achieved by post-linearization of the detected signal.

Contactless displacement transducer; eddy-currents; resonant impedance inversion; probe losses compensation; negative impedance converter (NIC); linear range extension; automatic resonance tuning

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