Surface acoustic wave scale

An electronic weighing apparatus for determining weight of a load, comprising:

• a displaceable elastic member that is displaced by the load such that displacement of the elastic member is related to the weight of the load;
• a first piezoelectric transducer comprising a first surface acoustic wave (SAW) transmitter spaced from a first SAW receiver, said first piezoelectric transducer being coupled to said elastic member;
• 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 electrically coupled to said first SAW transmitter such that said first SAW receiver, said first amplifier and said first SAW transmitter form a first delay line oscillator circuit that is configured to generate a first oscillating signal in response to displacement of said elastic member;
• a magnet spaced from a Hall effect sensor, wherein the magnet is configured to produce a magnetic field and the Hall effect sensor is configured to measure strength of the magnetic field which is related to displacement of said elastic member and the weight of the load;
• circuitry operably coupled to the first delay line oscillator circuit, wherein said circuitry is configured to generate first frequency data that characterizes frequency of said first oscillating signal, wherein the first frequency data is related to displacement of said elastic member and the weight of the load;
• a processor operably coupled to the circuitry and the Hall effect sensor, wherein said processor is configured to store calibration data for said electronic weighing apparatus, and wherein said processor is further configured to determine the weight of the load from at least the strength of the magnetic field measured by the Hall effect sensor, the calibration data and the first frequency data;
• and
• a push oscillator coupled to processor and to said first delay line oscillator circuit, wherein said push oscillator is configured to initiate oscillation of said first delay line oscillator circuit;
• wherein the processor is configured to determine whether the first delay line oscillator circuit is operating in a predefined desired mode based on the measurements of magnetic field performed by the Hall effect sensor, and selectively control the push oscillator to inject an oscillating voltage signal into the first delay line oscillator circuit such that first delay line oscillator circuit operates in the predefined desired mode in the event that the first delay line oscillator circuit is not operating in the predefined desired mode.