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Method and system for monitoring position of a fluid actuator employing microwave resonant cavity principles

  • US 4,689,553 A
  • Filed: 04/12/1985
  • Issued: 08/25/1987
  • Est. Priority Date: 04/12/1985
  • Status: Expired due to Fees
First Claim
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1. Apparatus for monitoring position of a piston within a cylinder comprisingmeans for generating microwave radiation over a preselected swept frequency range, antenna means coupled to said generating means and positioned in said cylinder to inject said microwave energy into said cylinder such that resonances of differing axial order and constant radial and circumferential orders of a single normal cylindrical mode of microwave propagation are developed within said cylinder as said generating means sweeps said frequency range, occurence-detecting means coupled to said antenna means for detecting occurrence of said resonances, and position-determining means responsive to said detecting means and to said generating means for determining position of said piston within said cylinder as a function of frequency of said microwave signal at which said resonances occur,characterized in that said position-determining means comprises means for identifying axial order of one said resonance, means coupled to said generating means for identifying microwave frequency associated with said one resonance, and means for determinig position of said piston within said cylinder as a combined function of said axial order and said frequency of said one resonance.

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