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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
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| 4,862,978 | Sept., 1989 | Borchard | |
| 4,862,979 | Sept., 1989 | Borchard | |
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| 4,960,177 | Oct., 1990 | Holm-Kennedy et al. | 177/210 C |
Primary Examiner: Miller, Jr.; George H.
Abstract
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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