Torque measuring apparatus and method employing a crystal oscillator
First Claim
1. An apparatus for measuring torque in a torsion member, that apparatus comprising:
- a transducer adapted to be attached to the torsion member and having a first resonant frequency which changes with variation of strain in the torsion member;
a transducer oscillator connected to the transducer and producing a first signal having a first frequency that is a function of the first resonant frequency;
a reference element having a second resonant frequency;
a reference oscillator connected to the reference element and producing a second signal having a second frequency that is a function of the second resonant frequency; and
a mixer connected to the transducer oscillator and to the reference oscillator to heterodyne the first signal and second signal thereby producing a resultant signal having a frequency which corresponds to torque applied to in the torsion member.
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Accused Products
Abstract
Torque in a torsion member, such as a rotating shaft, is sensed by a piezoelectric element that is attached to the torsion member. The piezoelectric element has a resonant frequency that varies with changes in the torque and is part of a transducer oscillator that produces a first signal. A reference oscillator has a similar piezoelectric element and produces a second signal having a frequency that varies in response to environmental parameters. The first and second signals are heterodyned, thereby cancelling the effects due to environmental parameters acting on both piezoelectric elements and producing a resultant signal that has a frequency which corresponds to the torque applied to the torsion member.
30 Citations
19 Claims
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1. An apparatus for measuring torque in a torsion member, that apparatus comprising:
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a transducer adapted to be attached to the torsion member and having a first resonant frequency which changes with variation of strain in the torsion member;
a transducer oscillator connected to the transducer and producing a first signal having a first frequency that is a function of the first resonant frequency;
a reference element having a second resonant frequency;
a reference oscillator connected to the reference element and producing a second signal having a second frequency that is a function of the second resonant frequency; and
a mixer connected to the transducer oscillator and to the reference oscillator to heterodyne the first signal and second signal thereby producing a resultant signal having a frequency which corresponds to torque applied to in the torsion member. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19)
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15. A method for measuring torque in a torsion member, that method comprising:
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attaching a transducer to the torsion member wherein the transducer has a first resonant frequency which varies with variation of strain in the torsion member;
exciting the transducer as part of a transducer oscillator to produce a first signal having a first frequency that is a function of the first resonant frequency;
driving a reference oscillator to produce a second signal having a second frequency; and
a heterodyning the first signal and second signal thereby producing a resultant signal having a frequency that indicates the torque in the torsion member.
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Specification