Simultaneously resonated, multi-mode crystal force transducer
First Claim
Patent Images
1. A force transducer comprising:
- a piezoelectric crystal having two opposite surfaces and a predetermined thickness, said surfaces lying generally along orthogonal axes determined from the structure and cut of the crystal, where a force applied to the crystal in the direction of one of said axis produces a shift in the crystals resonant frequency;
said crystal having at least two different electrode sets disposed on the surfaces of said crystal;
means for holding said crystal in a predetermined position, and for applying a received external force to said crystal at a predetermined angle with reference to said one axis;
first oscillator means connected to one of said two sets of electrodes for resonating said crystal at a first resonant frequency, said first resonant frequency being variable as a first function of the applied force;
second oscillator means connected to said other set of electrodes for resonating said crystal at a second resonant frequency indicative of an anharmonic resonant frequency having more than one resonant antinode lying in a direction angularly disposed to said one axis, said anharmonic resonant frequency being variable as a second function of the received force different from said first function;
means responsive to said first and second resonant frequencies for generating a signal indicative of the received force.
0 Assignments
0 Petitions
Accused Products
Abstract
The invention is a single crystal force transducer in which the crystal is simultaneously resonated in two different modes having substantially the same frequency-temperature characteristics and different frequency-force characteristics. The difference in the change between the two resonant frequencies with a force applied to the crystal is therefore a temperature compensated signal indicative of the applied force. In the preferred embodiment the two resonant modes are anharmonic modes having a plurality of antinodes angularly disposed to each other.
37 Citations
31 Claims
-
1. A force transducer comprising:
-
a piezoelectric crystal having two opposite surfaces and a predetermined thickness, said surfaces lying generally along orthogonal axes determined from the structure and cut of the crystal, where a force applied to the crystal in the direction of one of said axis produces a shift in the crystals resonant frequency;
said crystal having at least two different electrode sets disposed on the surfaces of said crystal;means for holding said crystal in a predetermined position, and for applying a received external force to said crystal at a predetermined angle with reference to said one axis; first oscillator means connected to one of said two sets of electrodes for resonating said crystal at a first resonant frequency, said first resonant frequency being variable as a first function of the applied force; second oscillator means connected to said other set of electrodes for resonating said crystal at a second resonant frequency indicative of an anharmonic resonant frequency having more than one resonant antinode lying in a direction angularly disposed to said one axis, said anharmonic resonant frequency being variable as a second function of the received force different from said first function; means responsive to said first and second resonant frequencies for generating a signal indicative of the received force. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
-
14. A force transducer comprising:
-
a piezoelectric crystal; means for applying a force to be determined to said piezoelectric crystal; first means for resonating said piezoelectric crystal in a first resonant mode having a first frequency-force characteristic to generate a first resonant frequency variable as a function of the applied force; second means for simultaneously resonating said same piezoelectric crystal in a second resonant mode having a second frequency-force characteristic different from said first frequency-force characteristic to generate a second resonant frequency variable as a function of the applied force; means responsive to said first and second resonant frequencies for generating a signal indicative of the applied force. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
-
-
23. A method for generating a signal proportional to an applied force comprising the steps of
applying a force to a piezoelectric crystal in a direction operative to change at least one of the crystal'"'"'s resonant frequencies; -
resonating said crystal in a first resonant mode having a first frequency-force characteristic to generate a first signal having a frequency variable as a function of the applied force; simultaneously resonating said crystal in a second resonant mode having a second frequency-force characteristic different from said first frequency-force characteristic to generate a second signal having a frequency variable as a function of the applied force; combining said first and second signals to generate a third signal indicative of the applied force. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31)
-
Specification