Linear position sensor with equalizing means
AssigneeCaterpillar Inc.
InventorDenny E. Morgan
Life of this patent
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Abstract
An apparatus is adapted to detect the linear extension, velocity and acceleration of a hydraulic cylinder. The hydraulic cylinder defines a variable length coaxial resonant cavity. Under the control of a controller, an RF transmitting section and an RF receiving section are used to determine the resonant frequency of the cavity. The receiving section includes an equalizer circuit for compensating for the insertion losses of the hydraulic cylinder. The linear extension of the cylinder is determined as a function of the resonant frequency.
Claims13
An apparatus for detecting a linear position of a piston and a piston rod being movable within a housing of a hydraulic cylinder, comprising:
- means for producing an electromagnetic signal and delivering said electromagnetic signal into said hydraulic cylinder, said electromagnetic signal having a frequency varying between predetermined minimum and maximum values;
- means for determining a resonant frequency of the hydraulic cylinder, said resonant frequency detecting means including means for sensing an electromagnetic wave signal within said hydraulic cylinder and equalizing said received electromagnetic signal, said equalization accounting for the losses of said hydraulic cylinder, comparing said equalized electromagnetic wave signal with a predetermined constant and responsively producing a frequency signal, said frequency signal being indicative of said resonant frequency;
- and
- means for receiving said frequency signal and responsively determining the position of said piston and piston rod.
An apparatus, as set forth in claim i, wherein said comparing means includes means for detecting the amplitude of said electromagnetic wave signal and responsively producing a detected signal.
An apparatus for detecting a linear position of a piston and a piston rod being movable within a housing of a hydraulic cylinder, comprising:
- means for producing an electromagnetic signal and delivering said electromagnetic signal into said hydraulic cylinder, said electromagnetic signal having a frequency varying between predetermined minimum and maximum values;
- means for determining a resonant frequency of the hydraulic cylinder, said resonant frequency detecting means including means for sensing an electromagnetic wave signal within said hydraulic cylinder and equalizing said received electromagnetic signal, said equalization accounting for the losses of said hydraulic cylinder, comparing said equalized electromagnetic wave signal with a predetermined constant and responsively producing a frequency signal;
- wherein said equalizing means includes:
- a transistor;
- a first voltage gain component, X.sub.c, connected between the collector and the base of said transistor;
- a second voltage gain component, X.sub.e, connected to the emitter of said transistor;
- wherein the overall voltage gain of said equalizing means is approximately X.sub.c /X.sub.e ;
- and
- means for receiving said frequency signal and responsively determining the position of said piston and piston rod.
Dependencies are inferred from the claim text.