Patent ID: 6812413
Filing Date: 2004-11-02
Classification: G01G

Abstract:
An electronic weighing apparatus, comprising:a) a displaceable elastic member means for receiving a load and being displaced by the load such that the displacement of said elastic member means is related to the weight of the load; b) a first piezoelectric transducer having a first substrate and one of a first surface acoustic wave (SAW) transmitter and a first SAW receiver, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and the other of said first SAW transmitter and said first SAW receiver, said second piezoelectric transducer being mounted in close proximity to said first piezoelectric transducer such that said displacement of said elastic member causes a corresponding displacement of one of said first and second piezoelectric transducers relative to each other; d) a first amplifier having an input and an output, said input of said first amplifier being coupled to said first SAW receiver and said output of said first amplifier being coupled to said first SAW transmitter such that said first piezoelectric transducer, said first amplifier, and said second piezoelectric transducer form a first oscillator having a first output frequency; e) processor means coupled to said output of said first amplifier; and f) sealing means covering said first and second piezoelectric transducers for sealing out moisture and other contaminants, wherein displacement of said elastic member means causes a displacement of one of said first and second piezoelectric transducers relative to each other and thereby changes said first output frequency, and said first output frequency is used by said processor means to determine an indication of the weight of the load.