US 6,581,478 B2 · Torque measuring apparatus and method employing a crystal oscillator

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.

Claims19

Dependent claims

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 that is unaffected by variation of strain in the torsion member;
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.

3 more elements

Dependencies are inferred from the claim text.

Torque measuring apparatus and method employing a crystal oscillator

Life of this patent

Torque measuring apparatus and method employing a crystal oscillator

Life of this patent

Abstract

Claims19