Electronic weighing apparatus utilizing surface acoustic waves

Claim 2

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, said elastic member having a hollowed central portion; b) a first piezoelectric transducer having a first substrate and a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member within said hollowed central portion; c) a second piezoelectric transducer having a second substrate and a 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; and e) processor means coupled to said output of said first amplifier, 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.

Claim 3

An electronic weighing apparatus according to claim 1, wherein: one of said first and second piezoelectric transducers is provided with anti-reflection structure to minimize reflection of surface acoustic waves.

Claim 4

An electronic weighing apparatus according to claim 2, wherein: said anti-reflection structure is one of a surface damper on said substrate, an angled cut on an end of said substrate, and a rounded end on said substrate.

Claim 5

An electronic weighing apparatus according to claim 1, further comprising: f) a third piezoelectric transducer having a second surface acoustic wave (SAW) transmitter, said third piezoelectric transducer being coupled to said elastic member within said hollowed central portion; g) a fourth piezoelectric transducer having a second SAW receiver, said fourth 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 third and fourth piezoelectric transducers relative to each other, said displacement being in a direction opposite to and in an amount substantially equal to said relative displacement of said first and second piezoelectric transducers relative to each other; h) a second amplifier having an input and an output, said input of said second amplifier being coupled to said second SAW receiver and said output of said second amplifier being coupled to said second SAW transmitter such that said third piezoelectric transducer, said second amplifier, and said fourth piezoelectric transducer form a second oscillator having a second output frequency, said output of said second amplifier being coupled to said processor means, wherein displacement of said elastic member means causes a displacement of one of said third and fourth piezoelectric transducers relative to each other and thereby changes said second output frequency by an opposite but substantially equal amount as said change in said first output frequency, said first and second output frequencies being used by said processor means to determine an indication of the weight of the load.

Claim 6

An electronic weighing apparatus according to claim 1, wherein: one of said first and second substrates is mounted on a thermal sink.

Claim 7

An electronic weighing apparatus according to claim 5, wherein: both of said first and second substrates are mounted on thermal sinks.

Claim 8

An electronic weighing apparatus according to claim 5, wherein: said thermal sink is mounted on a thermally insulating material.

Claim 9

An electronic weighing apparatus according to claim 1, wherein: one of said first and second transducers includes temperature sensing means on said substrate for determining the temperature of said substrate, said temperature sensing means being coupled to said processing means and said temperature being used by said processing means to determine an indication of the weight of the load.

Claim 10

An electronic weighing apparatus according to claim 8, wherein: said temperature sensing means includes a SAW transmitter and a SAW receiver.

Claim 11

An electronic weighing apparatus according to claim 8, wherein: said temperature sensing means is on said first substrate and comprises a SAW receiver.

Claim 12

An electronic weighing apparatus according to claim 8, wherein: said temperature sensing means is on said second substrate and comprises a SAW transmitter.

Claim 13

An electronic weighing apparatus according to claim 9, wherein: said temperature sensing means is located in the same acoustic channel as said first SAW transmitter.

Claim 14

An electronic weighing apparatus according to claim 1, further comprising: f) phase shift means coupled to said first amplifier for shifting the phase of said first output frequency by approximately 180°; and g) one of frequency and gain detection means coupled to said output of said first amplifier and coupled to said phase shift means for activating said phase shift means upon the detection of a predetermined one of frequency and gain.

Claim 15

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 a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and a 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; and e) processor means coupled to said output of said first amplifier, 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, and wherein one of said first and second piezoelectric transducers is provided with anti-reflection structure to minimize reflection of surface acoustic waves.

Claim 16

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 a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and a 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; and e) processor means coupled to said output of said first amplifier, 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, and wherein one of said first and second piezoelectric transducers is provided with anti-reflection structure to minimize reflection of surface acoustic waves.

Claim 17

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 a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and a 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 third piezoelectric transducer having a second surface acoustic wave (SAW) transmitter, said third piezoelectric transducer being coupled to said elastic member within said hollowed central portion; g) a fourth piezoelectric transducer having a second SAW receiver, said fourth 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 third and fourth piezoelectric transducers relative to each other, said displacement being in a direction opposite to and in an amount substantially equal to said relative displacement of said first and second piezoelectric transducers relative to each other; h) a second amplifier having an input and an output, said input of said second amplifier being coupled to said second SAW receiver and said output of said second amplifier being coupled to said second SAW transmitter such that said third piezoelectric transducer, said second amplifier, and said fourth piezoelectric transducer form a second oscillator having a second output frequency, said output of said second amplifier being coupled to said processor means, 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, and, wherein displacement of said elastic member means causes a displacement of one of said third and fourth piezoelectric transducers relative to each other and thereby changes said second output frequency by an opposite but substantially equal amount as said change in said first output frequency, said first and second output frequencies being used by said processor means to determine an indication of the weight of the load.

Claim 18

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 a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and a 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 third piezoelectric transducer having a second surface acoustic wave (SAW) transmitter, said third piezoelectric transducer being coupled to said elastic member within said hollowed central portion; g) a fourth piezoelectric transducer having a second SAW receiver, said fourth 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 third and fourth piezoelectric transducers relative to each other, said displacement being in a direction opposite to and in an amount substantially equal to said relative displacement of said first and second piezoelectric transducers relative to each other; h) a second amplifier having an input and an output, said input of said second amplifier being coupled to said second SAW receiver and said output of said second amplifier being coupled to said second SAW transmitter such that said third piezoelectric transducer, said second amplifier, and said fourth piezoelectric transducer form a second oscillator having a second output frequency, said output of said second amplifier being coupled to said processor means, 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, and, wherein displacement of said elastic member means causes a displacement of one of said third and fourth piezoelectric transducers relative to each other and thereby changes said second output frequency by an opposite but substantially equal amount as said change in said first output frequency, said first and second output frequencies being used by said processor means to determine an indication of the weight of the load.

Claim 19

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 a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and a 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; and e) processor means coupled to said output of said first amplifier, 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, and wherein one of said first and second transducers includes temperature sensing means on said substrate for determining the temperature of said substrate, said temperature sensing means being coupled to said processing means and said temperature being used by said processing means to determine an indication of the weight of the load.

Claim 20

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 a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and a 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; and e) processor means coupled to said output of said first amplifier, 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, and wherein one of said first and second transducers includes temperature sensing means on said substrate for determining the temperature of said substrate, said temperature sensing means being coupled to said processing means and said temperature being used by said processing means to determine an indication of the weight of the load.

Claim 21

An electronic weighing apparatus according to claim 16, wherein: said temperature sensing means includes a SAW transmitter and a SAW receiver.

Claim 22

An electronic weighing apparatus according to claim 16, wherein: said temperature sensing means is on said first substrate and comprises a SAW receiver.

Claim 23

An electronic weighing apparatus according to claim 16, wherein: said temperature sensing means is on said second substrate and comprises a SAW transmitter.

Claim 24

An electronic weighing apparatus according to claim 17, wherein: said temperature sensing means is located in the same acoustic channel as said first SAW transmitter.

Claim 25

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 a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and a 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; f) phase shift means coupled to said first amplifier for shifting the phase of said first output frequency by approximately 180°; and g) one of frequency and gain detection means coupled to said output of said first amplifier and coupled to said phase shift means for activating said phase shift means upon the detection of a predetermined one of frequency and gain, 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.

Claim 26

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 a first surface acoustic wave (SAW) transmitter, said first piezoelectric transducer being coupled to said elastic member; c) a second piezoelectric transducer having a second substrate and a 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; f) phase shift means coupled to said first amplifier for shifting the phase of said first output frequency by approximately 180°; and g) one of frequency and gain detection means coupled to said output of said first amplifier and coupled to said phase shift means for activating said phase shift means upon the detection of a predetermined one of frequency and gain, 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.