Patent
Digital BFO metal detecting device with improved sensitivity at near-zero beat frequencies
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TLDR
In this paper, an improved metal detecting device of the beat frequency oscillator type is provided, which incorporates a method for determining the side of the zero beat frequency at which a search oscillator is operating.Abstract:
An improved metal detecting device of the beat frequency oscillator type is provided which incorporates a method for determining the side of the zero beat frequency at which a search oscillator is operating. The device includes a search coil conveniently mounted which is part of a search oscillator. A reference oscillator is also provided, the output of which is digitally compared to that of the search oscillator by a digital phase comparator. The digital phase comparator output is applied through a low pass filter to a slope detector circuit. The slope detector output signal is supplied to both an audio output circuit and a filter/comparator. The audio output is sufficient to facilitate location of permeable and conductive substances. The output of the slope detector also contains information which is extracted by the filter/comparator and translated to an audible signal by an oscillator and the audio output circuit. This audible signal serves to facilitate the determination of whether a permeable or a conductive substance is being detected.read more
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TL;DR: A magnetic detection device including at least one oscillator circuit having a magnetoresistance element which converts a change of magnetism detected into a digital signal and a comparator for comparing the digitalized oscillating frequency of the oscillator circuits with another digitalised oscillation frequency generated from another oscillating circuit by taking a ratio thereof or by detecting a phase difference between the pulse signals.
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References
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Patent
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TL;DR: In this paper, a surgical metal body locator adapted to serve, alone or as an adjunct to known X-ray and fluoroscope means, for locating metal bodies in living tissue.
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