Span adjusting method and apparatus
AssigneeKabushiki Kaisha Ishida Koki Seisakusho
InventorSetsuo Haze
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Abstract
A span adjustment method includes applying a known load to a weighing machine and converting an output value from the weighing machine into a digital value by using an analog-to-digital converter. The characteristic of the analog-to-digital converter is sequentially varied automatically by a span adjustment value, which is produced as an output by a control unit, so that the digital value resulting from the analog-to-digital conversion becomes a digital value set in the control unit and conforming to the known load.
Claims10
A span adjustment method for applying a known load to a weighing machine which produces an analog output, and effecting an adjustment so that a true weight value, in the form of a digital value conforming to the known load, is obtained, said method comprising the steps of:
- (a) producing a digital span adjustment value;
- (b) converting the digital span adjustment value into an analog span adjustment value;
- (c) converting the analog output of the weighing machine into a digital output value using an analog-to-digital converter, and comparing the digital output value and the digital value conforming to the known load, while changing a conversion characteristic of the analog-to-digital converter in accordance with the analog span adjustment value;
- and
- (d) sequentially changing the digital span adjustment value, in accordance with the relative sizes of the compared digital values, to obtain a true weight value, which conforms to the known load, as the digital output value produced as an output by the analog-to-digital converter.
A span adjustment apparatus for applying a known load to a weighing machine which produces an analog output, and effecting an adjustment so that a true weight value, in the form of a digital value conforming to the known load, is obtained, said apparatus comprising:
- an analog-to-digital converter, operatively connected to the weighing machine and having a variable analog-to-digital conversion characteristic, for converting the analog output of the weighing machine into a digital output value;
- first means for storing a span adjustment value for adjusting the variable analog-to-digital conversion ' characteristic of said analog-to-digital converter;
- second means for storing the digital value conforming to the known load;
- comparison means, operatively connected to said second means and said analog-to-digital converter, for comparing the digital value conforming to the known load and the digital output value from said analog-to-digital converter;
- and
- means, operatively connected to said first means and said comparison means, for sequentially changing the span adjustment value in accordance with the relative sizes of the digital values compared by said comparison means to obtain a true weight value, which conforms to the known load, as the digital output value from said analog-to-digital converter.
A span adjustment apparatus for applying a known load to a weighing machine which produces an analog weight signal and effecting an adjustment so that a true weight value, in the form of a digital value conforming to the known load, is obtained, said apparatus comprising:
- a sequential comparison-type analog-to-digital converter, operatively connected to the weighing machine, for converting the analog weight signal into a digital weight value;
- a control unit, operatively connected to said sequential comparison type analog-to-digital converter, for comparing the digital weight value produced as an output by said sequential comparison type analog-to-digital converter, and the digital value conforming to the known load, for varying a span adjustment value in accordance with the relative sizes of the compared digital values, and for providing the varied span adjustment value in the form of a digital span adjustment value;
- a span adjustment digital-to-analog converter, operatively connected to said control unit, for converting the digital span adjustment value provided by said control unit into an analog span adjustment value;
- and
- voltage dividing and shifting means, operatively connected to said span adjustment digital-to-analog converter and said sequential comparison type analog-to-digital converter, for dividing the voltage of the analog span adjustment value output by said span adjustment digital-to-analog converter, for adding a predetermined voltage to the divided analog span adjustment output voltage and for delivering the result as an analog span adjustment voltage to said sequential comparison type analog-to-digital converter.
A span adjustment method for use with a weighing machine which produces an analog weight value in dependence upon the load thereon, comprising the steps of:
- (a) applying a load having a predetermined weight value corresponding to a predetermined digital value to the weighing machine;
- (b) providing a digital span adjustment value having an initial value;
- (c) converting the digital span adjustment value into an analog span adjustment value;
- (d) converting the analog weight value to a digital output value in dependence upon a conversion characteristic which is varied in accordance with the analog span adjustment value;
- (e) comparing the digital output value to the predetermined digital value;
- (f) adjusting the digital span adjustment value to vary the conversion characteristic used in said step (d);
- and
- (g) repeating said steps (c) through (f) until the digital output value is equal to the predetermined digital value or until said comparing step (e) has taken place k times, where k is an integer greater than one.
Dependencies are inferred from the claim text.