Linear position sensor using a coaxial resonant cavity

Reference Number: N 01-03

Inventors: Bitar, Ali A.; Morgan, Denny E.; Bowman, Charles W.

USPTO Link: 5438274

Invention Summary

In one aspect of the present invention, an apparatus for detecting a linear position of a piston and a piston rod is provided. The piston and piston rod are movable within a housing and define a variable length coaxial resonant cavity. A transmitting section produces an electromagnetic signal and delivers the electromagnetic signal into the resonant cavity. The electromagnetic signal has a frequency which varies between predetermined minimum and maximum values. A receiving section senses an electromagnetic wave signal within the coaxial cavity and detects a slope intercept condition of the electromagnetic wave signal. A sensor controller determines the position of the piston and piston rod as a function of the slope intercept condition.

In another aspect of the present invention, a method for detecting a linear position of a piston and a piston rod is provided. The piston and piston rod are movable within a housing and define a variable length coaxial resonant cavity. The method includes the steps of delivering an electromagnetic signal into the coaxial resonant cavity, receiving electromagnetic wave signals from said coaxial resonant cavity, detecting a slope intercept condition and responsively determining the position of the piston and piston rod.