Method and apparatus for scale calibration and weighing

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.

Claim 2

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.

Claim 6

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: (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.

Claim 7

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: (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.