Differential variable reluctance transducer

• US 5,497,147 A
• Filed: 06/21/1993
• Issued: 03/05/1996
• Est. Priority Date: 06/21/1993
• Status: Expired due to Term

• Current Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Original Assignee: MicroStrain, Inc. (Spectris PLC)
• Inventors: Arms, Steven W., Townsend, Christopher P.
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): Wu, Daniel J.
• Application Number:
  US08/078,467
• Time in Patent Office: 988 Days
• Field of Search: 340/870.31, 340/870.32, 340/870.33, 340/870.35, 340/539, 340/870.36, 324/207.15-207.19
• US Class Current: 340/870.35
• CPC Class Codes: G01B 7/24 using change in magnetic properties
• CPC Class Codes: G01D 5/2216 by a movable ferromagnetic element, e.g. a core

Abstract

The novel differential variable reluctance transducer and telemetry system is comprised of a ultra miniaturized device encased in stainless steel. The system contains a free sliding, magnetically permeable, stainless core and two coils surrounding the core. The position of the core is detected by measuring the coils'"'"' differential reluctance. The coils resonate at a frequency which depends on the position of the core and the difference in resonant frequency is used to modulate a high frequency carrier. This radio frequency signal is transmitted for remote reception by an FM receiver, amplified and put through a phase-locked-loop circuit into a microprocessor for counting and displaying.

Claims

1. Differential variable reluctance transducer and telemetry system, for use in industrial and medical research applications to measure strains in areas previously considered inaccessible, comprising:

a housing;

said housing comprising a hollow tubular structure;

said housing further comprising a stainless steel tube;

said housing having positioning means attached at least one end of said housing;

said housing further having removal means attached;

slideable core means located within said housing;

said slideable core means having positioning means attached;

said slideable core means further having removal means attached;

said slideable core means comprising a magnetically permeable metallic center;

said permeable metallic center having a circumference of stainless steel;

a plurality of coils surrounding said slideable core means;

said coils having implanting means for positioning said coils within said housing;

said coil implanting means comprising potting said coils in epoxy;

said coils further having circuitry means attached thereto;

said circuitry means comprising wire means;

said wire means having flexible polymeric means surrounding said wire means for permitting protection and flexibility;

said circuitry means having signal sending means attached;

said signal sending means comprising a transmitting system;

said transmitting system comprising oscillators attached to each of said coils for controlling the frequency of resonance of said coils;

said transmitting system further comprising a mixing circuit for producing the frequency difference between said coils;

said transmitting system further comprising a high frequency oscillator for wireless data transmission which is modulated by said frequency differences;

said transmitting system further comprising an FM antenna; and

said circuitry means further comprising a receiving system for receiving a signal from said FM antenna.

2. Differential variable reluctance transducer and telemetry system, according to claim 1, wherein:

said receiving system comprises an FM receiver;

said receiving system further comprises an amplifier for increasing the volume of the signal;

said receiving system further comprises a phase-locked-loop circuit for tracking and clarifying the signal;

said receiving system further having a microprocessor for counting and evaluating the signal.

3. Differential variable reluctance transducer and telemetry system, according to claim 2, wherein:

said microprocessor having display means; and

said microprocessor further having storage means.