Robert A Mathews

US Patent:

6581478, Jun 24, 2003

Filed:

Jul 5, 2001

Appl. No.:

09/898817

Inventors:

Birger Pahl - Milwaukee WI
James E. Hansen - Oak Creek WI
Matthew F. Planning - Milwaukee WI
Robert H. Mathews - Decatur IN

Assignee:

Eaton Corporation - Cleveland OH

International Classification:

G01L 302

US Classification:

73862326, 73862325, 7386208, 73DIG 4

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.