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United States Patent 5,183,124
Borchard Feb. 2, 1993

Compact self-adjusting weighing system having stable measurement resolution

Inventors: Borchard; John (97A Lowell Ave., Newton, MA 02160).
Appl. No.: 578,461
Filed: Sept. 7, 1990
Intl. Cl.: G01G 3/14;
U.S. Cl.: 177/210.FP;
Field of Search: 210 FP

References Cited

U.S. Patent Documents

3,922,670 Nov., 1975 Shaw et al.
3,966,002 Jun., 1976 Schneider
4,051,721 Oct., 1977 Williams
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4,237,989 Dec., 1980 Lewis
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4,366,875 Jan., 1983 Dauge et al. 177/210 FP
4,405,024 Sept., 1983 Fraval et al.
4,405,025 Aug., 1983 Yanagita et al.
4,464,725 Aug., 1984 Briefer
4,503,922 Aug., 1984 Brosh
4,738,324 Apr., 1988 Borchard
4,814,692 Mar., 1989 Baumann
4,828,057 May, 1989 Borchard
4,858,145 Aug., 1989 Inoue et al.
4,858,145 Aug., 1989 Inoue et al.
4,862,978 Sept., 1989 Borchard
4,862,979 Sept., 1989 Borchard
4,869,331 Sept., 1989 Borchard
4,874,051 Oct., 1989 Borchard
4,960,177 Oct., 1990 Holm-Kennedy et al. 177/210 C

Primary Examiner: Miller, Jr.; George H.


A weighing system and method having stable measurement resolution for measuring gems and other light masses. The system includes circuitry for correcting errors in the measured value of the masses due to off-center placement on the system's holding pan. The weighing system uses a plurality of transducers about the pan to measure the weight of the mass, and includes circuitry for converting the transducer signals to signals having unknown frequencies. Circuitry is also provided for determining the unknown frequencies with an approximate stable or fixed resolution, despite wide variations in the unknown frequency. In a preferred embodiment, the number of cycles on the unknown frequency is counted and counting begins and ends of the rising edges of the unknown frequency signal. The determination of which unknown frequency edge ends the counting operation is made by monitoring a known frequency counter. When a predetermined minimum number of known frequency cycles have been accumulated, the next rising edge of the unknown frequency signal terminates the counting operation. The unknown frequency is then calculated. Finally, the frequencies from each sensor are correlated for a given mass, at given locations, to arrive at an accurate weight value for the mass in spite of its potentially off-center location on the system's weighting pan.

26 Claims, 7 Drawing Figures

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