Method and apparatus for scale calibration and weighing
First Claim
1. A method for calibrating an electronic scale having a plurality of load cells for supporting a weighing platform and for generating a voltage proportional to the response of each load cell to the application of a weight to said platform, a corresponding plurality of amplifiers coupled to said load cells, a multiplexer coupled to said amplifiers for sequentially receiving said voltages from said amplifiers, an analog-to-digital converter coupled to said multiplexer for converting voltages representative of load cell responses received from said multiplexer to digital values, microprocessor means coupled to said analog-to-digital converter for receiving and utilizing said digital values, and a display controlled by said microprocessor means, said method comprising the following steps:
- (a) performing a test operation without weight on said weighing platform to determine whether said scale is properly calibrated to zero weight;
(b) if said scale is not properly calibrated to zero weight, operating a calibration switch to initiate a calibration operation;
(c) displaying on said display an instruction to the scale operator to place predetermined test weights at predetermined positions on the weighing platform;
(d) performing a plurality of weighing operations equal in number to the number of load cells and for each weighing operation obtaining a digital value representing the response of each load cell;
(e) solving by said microprocessor means a plurality of simultaneous equations equal in number to the number of load cells to derive a plurality of constants, one of said constants being associated with each of the said load cells;
(f) storing said plurality of constants in a memory included in said microprocessor means for use in future weighings by said electronic scale; and
(g) operating said calibration switch to terminate the calibration operation.
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Accused Products
Abstract
A scale utilizes a plurality of load cells positioned beneath a weighing platform for determining the weight of objects placed upon the platform. During a weighing operation, each load cell generates a voltage proportional to the response of said cell to the application of a weight to the platform. Each such generated voltage is transmitted serially through a multiplexer and is converted to a digital value by an analog-to-analog converter. These digital values are employed by a microprocessor to determine the weight of the object placed on the weighing platform. The scale is calibrated by weighing a test weight in a plurality of different locations on the weighing platform, and utilizing the individual digital values thus obtained for each load cell in a plurality of simultaneous equations, which are then solved in the microprocessor to provide constant values associated with each load cell, which are used in subsequent weighing operations.
104 Citations
16 Claims
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1. A method for calibrating an electronic scale having a plurality of load cells for supporting a weighing platform and for generating a voltage proportional to the response of each load cell to the application of a weight to said platform, a corresponding plurality of amplifiers coupled to said load cells, a multiplexer coupled to said amplifiers for sequentially receiving said voltages from said amplifiers, an analog-to-digital converter coupled to said multiplexer for converting voltages representative of load cell responses received from said multiplexer to digital values, microprocessor means coupled to said analog-to-digital converter for receiving and utilizing said digital values, and a display controlled by said microprocessor means, said method comprising the following steps:
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(a) performing a test operation without weight on said weighing platform to determine whether said scale is properly calibrated to zero weight; (b) if said scale is not properly calibrated to zero weight, operating a calibration switch to initiate a calibration operation; (c) displaying on said display an instruction to the scale operator to place predetermined test weights at predetermined positions on the weighing platform; (d) performing a plurality of weighing operations equal in number to the number of load cells and for each weighing operation obtaining a digital value representing the response of each load cell; (e) solving by said microprocessor means a plurality of simultaneous equations equal in number to the number of load cells to derive a plurality of constants, one of said constants being associated with each of the said load cells; (f) storing said plurality of constants in a memory included in said microprocessor means for use in future weighings by said electronic scale; and (g) operating said calibration switch to terminate the calibration operation. - View Dependent Claims (2, 3, 4)
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5. A method for weighing an object, using an electronic scale having a plurality of load cells for supporting a weighing platform and for generating a voltage proportional to the response of each load cell to the application of a weight to said platform, a corresponding plurality of amplifiers coupled to said load cells, a multiplexer coupled to said amplifiers for sequentially receiving said voltages from said amplifiers, an analog-to-digital converter coupled to said multiplexer for converting voltages representative of load cell responses received from said multiplexer to digital values, microprocessor means coupled to said analog-to-digital converter for receiving and utilizing said digital values, and a display controlled by said microprocessor means, said method comprising the following steps:
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(a) performing a test operation without weight on said weighing platform to determine whether said scale is properly calibrated to zero weight; (b) if said scale is not properly calibrated to zero weight, operating a calibration switch to initiate a calibration operation; (c) displaying on said display an instruction to the scale operator to place predetermined test weights at predetermined positions on the weighing platform; (d) performing a plurality of weighing operation equal in number to the number of load cells and for each weighing operation obtaining a digital value representing the response of each load cell; (e) solving by said microprocessor means a plurality of simultaneous equations equal in number to the number of load cells to derive a plurality of constants, one of said constants being associated with each of said load cells; (f) storing said plurality of constants in a memory included in said microprocessor means for use in future weighings by said electronic scale; (g) operating said calibration switch to terminate the calibration operation; (h) proceeding with a weighing operation for determining an unknown weight by placing the object to be weighed on the weighing platform and obtaining a value for each of the load cells; and (i) solving by said microprocessor means an equation using the load cell values and the constants which were obtained in step (e) and stored in a memory in step (f), to determine the unknown weight. - View Dependent Claims (6, 7, 8, 9, 10)
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11. Apparatus for calibration of an electronic scale comprising:
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a weighing platform for receiving an object whose weight is to be determined; a plurality of load cells supporting said weighing platform and capable of producing a change in electrical signal in response to a change of weight on said platform; a plurality of amplifiers, each associated with on of said load cells, to amplify the electrical signals produced by said load cells; a multiplexer coupled to said amplifiers for sequentially receiving said amplified signals from said load cells; an analog-to-digital converter coupled to said multiplexer for sequentially receiving said signals relating to said load cells from said multiplexer and digitizing them; and microprocessor means coupled to said analogto-digital converter for receiving and utilizing said digitized signals in the solution of simultaneous equations to develop constants which are associated with the various load cells in the weighing of objects by said electronic scale, said microprocessor means being coupled to said multiplexer for control of said multiplexer. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification