Patent ID: 7533799

Claim:
A method for determining a fault condition in a weight scale comprising: obtaining weight data including a mean weight M n and a standard deviation SD n for each item n of a plurality of items 1 through N being weighed at the weight scale during a common transaction; individually measuring a weight W n of each of the items n at the weight scale during the transaction; calculating an error E n for each the weights W n relative to the weight data according to the following equation: E n =( W n − M n )/ SD n ; determining an accumulated error as a function of the error E n for each of the weights W n , including summing all of the errors E n for all of the items n during the common transaction and calculating an average value E ave for the absolute value or magnitude of each of the errors E n for all of the items n during the common transaction; and indicating a fault condition of the weight scale if the accumulated error exceeds a threshold including comparing the accumulated error to a first threshold and the average value E ave to a second threshold.