Importance

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Abstract

A system includes an oscillator for exciting an eddy current coil at one or more frequencies, detector circuitry for processing coil output signals and a balance and control calibration unit connected with the oscillator and the detector circuitry for so operating upon coil output signals in the detector circuitry as to force operation of the detector circuitry into a prescribed subrange of its overall operation range, and to effect correction of nonlinearity parameters bearing on system accuracy. The system is multi-frequency in makeup, the coil being excited at plural frequencies and the detector circuitry including separate detector channels corresponding respectively with the coil excitation frequencies. The coil output signals can be monitored in the detector channels for the occurrence in one or more of the channels of peaking of the coil output signal to a given magnitude above a threshold level. On this event, samples of the coil output signals are taken in each detector and the system conveys the sampled signals or the continuous detector output signals to a microprocessor for particularized gathering of intelligence from the sampled signals. Such microprocessor also may operate the system at large.

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First Claim