Electronic weighing apparatus utilizing surface acoustic waves
AssigneeCircuits & Systems, Inc.
InventorsVyacheslav D. Kats, Arnold s. Gordon
Life of this patent
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Abstract
A weighing apparatus which includes a SAW oscillator (120b, 122b) and a “push oscillator” (216, 218, 220) to force the SAW oscillator into a desired mode of operation. The device adjusts to temperature by using a temperature sensing SAW transducer assembly (124, 126). Long term temperature stability of the SAW frequency oscillator is achieved by periodic calibration with a thermistor (224) signal.
Claims31
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) a push oscillator coupled to said first SAW receiver for altering said first output frequency, 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.
An electronic apparatus for measuring displacement, comprising:
- a) a first piezoelectric transducer having a first substrate and one of a first surface acoustic wave (SAW) transmitter and a first SAW receiver;
- b) 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;
- c) 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;
- d) processor means coupled to said output of said first amplifier;
- and
- e) a push oscillator coupled to said first SAW receiver for altering said first output frequency, wherein
- 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 magnitude of the displacement.
A method for improving the phase linearity of a SAW wave oscillator in an electronic weighing apparatus having a first amplifier having an input coupled to a first SAW receiver and an output coupled to a first SAW transmitter, said method comprising:
- periodically injecting an RF signal into the first SAW receiver in order to change the mode of oscillation to the mode having the best phase linearity.
A method for improving the phase linearity of a SAW wave oscillator in an electronic apparatus for measuring displacement having a first amplifier having an input coupled to a first SAW receiver and an output coupled to a first SAW transmitter, said method comprising:
- periodically injecting an RF signal into the first SAW receiver in order to change the mode of oscillation to the mode having the best phase linearity.
A weighing apparatus, comprising:
- a) a first SAW sensor including a first SAW transmitter and a first SAW receiver;
- b) a second SAW sensor including a second SAW transmitter and a second SAW receiver;
- c) a displaceable member, at least one of said first and second SAW sensors being coupled to said displaceable member such that displacement of said displaceable member results in displacement of one of said transmitter and receiver relative to the other,
- d) a amplifier having an input and an output, both of said SAW sensors being coupled in parallel to said amplifier, wherein
- said first SAW sensor is arranged to oscillate at a first frequency and said second SAW sensor is arranged to oscillate at a second frequency different from said first frequency.
A push oscillator for use with a first SAW oscillator to force the first SAW oscillator into a desired mode of operation:
- a) a temperature sensing oscillator having a first output;
- b) a fixed frequency oscillator having a second output;
- and
- c) a mixer having two inputs and a third output, wherein
- said first and second outputs are coupled to respective of said two inputs and said third output forms the output if said push oscillator.
A weighing apparatus, comprising:
- a) a displaceable member;
- b) a first SAW oscillator coupled to said displaceable member such that displacement of said displaceable member causes a change in the frequency of said first SAW oscillator;
- c) a second SAW oscillator coupled to said displaceable member such that displacement of said displaceable member causes a change in the frequency of said second SAW oscillator;
- wherein
- the frequency of said first SAW oscillator and the frequency of said second SAW oscillator are different.
Dependencies are inferred from the claim text.