System and method for fast weighing of items such as mailpieces

Abstract

A system and method for fast weighing of items such as mailpieces. The system includes a scale system having a platform connected to a load cell that provides an output signal to an analog-to-digital converter. The resulting digital output signal is processed by a low pass filter and analyzed by a microprocessor to determine weights of items on the platform. The microprocessor also determines postage amounts of items on the platform. The microprocessor also determines postage amounts as functions of the weights and outputs these postage amounts to a postage meter. The microprocessor determines the weights as the median of the peak to valley difference of the digital output signal when the digital output signal peak to valley difference is less than a predetermined value. The microprocessor identifies peaks and valleys of the digital output signal by determining when the derivative of the signal changes sign. The microprocessor uses the determined first peak value to determine if the weight is below the first weight break point. The microprocessor also estimates the weight as an average of a sum of medians for N preceding cycles if the digital output signal does not converge. The postage meter initially assumes that all mailpieces have a minimum postage amount due and corrects the postage amount when a weight signal is received from the microprocessor so as to take advantage of the fact that the majority of mailpieces require only a minimum postage amount.