Hysteresis-compensated weighing apparatus and method
AssigneeMettler-Toledo AG
InventorNeil C. Griffen
Life of this patent
Estimating the term…
Abstract
A digital scale is compensated for hysteresis by characterizing an envelope pattern of increasing and decreasing linearity attributes thereof defining the limits of hysteresis error. Polynomial expressions define this envelope pattern and a correction procedure is developed which is based upon offsets from the envelope pattern as well as the merging characteristics of deviations evidenced from complex loading histories. The latter historical data are used to identify loading progression transitions necessary for the generation of correction values.
Claims19
The method for correcting the output of an electronic weighing scale for hysteresis effects occurring between minimum and maximum loads applied thereto with a given load progression history comprising the steps of:
- storing a derived polynomial expression representing the increasing linearity characteristic values of said scale extending from said minimum to said maximum loads;
- storing a derived polynomial expression representing the decreasing linearity characteristic values of said scale extending from said maximum to said minimum loads;
- storing an increasing weight correction expression incorporating said increasing linearity polynomial expression and representing an offset therefrom;
- storing a decreasing weight correction expression incorporating said decreasing linearity polynomial expression and representing an offset therefrom;
- obtaining a representation of value, R, of a load applied to said scale;
- comparing said representation of value, R, with the previous such representation, PR;
- determining said offset for said previous representation, PR, as a value WO, when said value, R, represents a reversal of said load progression;
- deriving a correction value as an application of said values, R and WO, to one of said correction expressions;
- adjusting said value, R, by the amount of said correction value;
- and
- outputing said adjusted value.
Weighing apparatus compensated for hysteresis effects occurring between minimum and maximum loads applied thereto with a given load progression history, comprising:
- a weighing mechanism;
- means for storing predetermined expressions representing the increasing and decreasing deviation linearity characteristics of said weighing mechanism extending between said minimum and maximum loads;
- means for storing increasing and decreasing weight correction expressions incorporating said increasing and decreasing linearity characteristics, respectively, and representing offsets therefrom;
- means for obtaining a representation of value, R, of a load applied to said weighing mechanism;
- means for comparing said representation of value, R, with a previous such representation, PR;
- means for determining said offset for said previous representation, PR, as a value, W0, when said value, R, represents a reversal of said load progression;
- means for deriving a correction value applying said values, R and W0, to one of said weight correction expressions;
- means for adjusting said value, R, by the amount of said correction value;
- and
- means for outputting said adjusted value.
Dependencies are inferred from the claim text.