Importance

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Abstract

A zero tracking circuit (32) monitors the output of an electronic scale employing a dual slope integrating type analog-to-digital converter (20) to detect low magnitude output signal levels characteristic of drift and other low level noise. The converter (20) samples the magnitude of an input analog signal proportional to applied weight and in response controls a count accumulated in a resettable up/down counter (36). The counter (36) is manually reset to provide tare, that is, to provide a zero reading with an applied weight. The output of the counter (36) is supplied to a digital display (40a-40d) that displays changes in applied weight. The zero tracking circuit (32) includes a decoder (56) that monitors the output of the counter (36) and in response to low magnitude counts characteristic of drift, e.g., one count on each side of zero, resets the counter (36) to eliminate the drift.

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First Claim