Method and apparatus for measuring weight using uncalibrated load cells
First Claim
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1. A measuring and calibration method comprising the steps of:
- installing at least two load sensing devices onto a load carrying device, said at least two load sensing devices each having an individual output signal;
connecting said individual output signal from each of said at least two load sensing devices to a computing device;
analyzing a first set of values and a second set of values of said individual output signals from each of said at least two load sensing devices; and
calibrating said at least two load sensing devices responsive to said analysis of said output signals of said at least two load sensing devices;
estimating a weight of a substance in said load carrying device; and
gradually removing said substance from said load carrying device while monitoring and determining relative rates in change of said individual output signals to calculate an associated relative scale factor for each individual load sensing device.
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Abstract
A method and apparatus for calibrating load cells in the filed after the uncalibrated load cells have been installed. Two known weight conditions are used in conjunction with a storage device in which the uncalibrated load cells are installed. The method will calibrate the load cells, calculate load cell offsets, scale factor differences between load cells, and flexure/stresses in a supporting structure which rests upon the uncalibrated load cells.
36 Citations
22 Claims
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1. A measuring and calibration method comprising the steps of:
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installing at least two load sensing devices onto a load carrying device, said at least two load sensing devices each having an individual output signal;
connecting said individual output signal from each of said at least two load sensing devices to a computing device;
analyzing a first set of values and a second set of values of said individual output signals from each of said at least two load sensing devices; and
calibrating said at least two load sensing devices responsive to said analysis of said output signals of said at least two load sensing devices;
estimating a weight of a substance in said load carrying device; and
gradually removing said substance from said load carrying device while monitoring and determining relative rates in change of said individual output signals to calculate an associated relative scale factor for each individual load sensing device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
where; Ci=the scale factor for load cell “
i”
;
N100i=the reading from the ith load cell at substantially full load;
N90i=the reading from the ith load cell at substantially 90% of full load; and
n=the number of load cells.
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19. The measuring and calibration device of claim 17 wherein the step of estimating said weight of said substance within said load carrying device includes using the following equation:
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where; δ
Ni=Ni-NMinCal— i;
NMinCal — i=the reading from the ith load cell at the Minimum Calibration;
NMaxCal — i=the reading from the ith load cell at the Maximum Calibration;
Ci=the scale factor for the ith load cell, as calculated above;
WMaxCal=the weight entered by the user at full load during Maximum Calibration; and
WMinCal=the weight entered by the user at no load during Minimum Calibration.
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20. A method for weight calibration and measurement comprising the steps of:
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installing at least two load sensing devices onto a load carrying device, said at least two load sensing devices each having an output signal;
connecting said output signals from each of said at least two load sensing devices to a computing device;
analyzing a first set of output signal values and a second set of output signal values;
calibrating said at least two load sensing devices responsive to said analysis of said output sets of signals by solving the equation
where;
Ci=the scale factor for load cell “
i”
;
N100i=the reading from the ith load cell at substantially full load;
N90i=the reading from the ith load cell at substantially 90% of full load; and
n=the number of load cells;
to calculate a scale factor for each of said at least two load sensing devices by solving the following equation
where;
δ
Ni=Ni-NMinCal— i;
NMinCal — i=the reading from the ith load cell at the Minimum Calibration;
NMaxCal — i=the reading from the ith load cell at the Maximum Calibration;
Ci=the scale factor for the ith load cell, as calculated above;
WMaxCal=the weight entered by the user at full load during Maximum Calibration; and
WMinCal=the weight entered by the user at no load during Minimum Calibration;
to calculate a weight of said substance within the load carrying device.
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21. An apparatus for measurement and calibration comprising:
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a load carrying device;
at least two load sensing indicators used with the load carrying device, said at least two load sensing indicators each configured to provide an output signal; and
a computing device, said computing device being configured to (a) analyze said output signals to calculate a weight of a substance in said load carrying devices;
(b) to calculate a scale factor for each of said at least two load indicators; and
(c) to calculate said scale factor for each of said at least two load indicators by identifying relative rates of change of said output signals during a removal of said substance from said load carrying device.
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22. A measuring and calibration method comprising the steps of:
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installing at least two load sensing devices onto a load carrying device, said at least two load sensing devices each having an individual output signal;
establishing an initial calibration for each of said at least two load sensing devices;
altering a load in said load carrying device while monitoring said individual output signals to determine relative rates in change of said individual output signals;
calculating an associated relative scale factor for each individual load sensing device based on said determined relative rates of change; and
utilizing each of said associated relative scale factors to establish a final calibration for each of said at least two load sensing devices.
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Specification