Linear displacement transducer utilizing an oscillator whose average period varies as a linear function of the displacement

Claim 2

In an apparatus for measuring a dimensional quantity, in combination a variable inductor comprising an inductive coil, means interfacing with a portion of the length of said coil, said means axially movable in a direction parallel to the axis of said coil, and varying the inductance of said coil as a square function of the relative axial displacement of said coil and said means interfacing, and means mechanically coupling to the measured dimensional quantity and effecting said relative axial displacement; a variable oscillator comprising in part said variable inductor and controlled at least in part thereby, and producing a periodic output time-varying in proportion to said relative axial displacement; and means receiving said periodic output and measuring the period thereof relative to a suitable reference, and yielding therefrom a measure of said dimensional quantity.

Claim 3

A transducer system for measuring a dimensional quantity, comprising a variable inductor having at least two partially interfacing parts, at least one of said parts being fixed and at least one of said parts being axially displaceable, each of said parts being of nearly uniform composition and cross-sectional area; said variable inductor having an inductance varying as a square function of an axial displacement of at least one of said parts; at least one capacitor connected in parallel with said variable inductor forming a resonant circuit whose period varies as a square-root function of inductance; a variable oscillator frequency-controlled by said resonant circuit, said oscillator producing an alternating current whose period varies as a linear function of said axial displacement by combination of said square function and said square-root function; means connecting a direct-current input to said variable oscillator; means taking a periodic-current output from said variable oscillator; and means receiving said periodic-current output and measuring the relative period thereof producing a proportional measure of the axial displacement of said axially displaceable part.

Claim 4

A transducer system for measuring a dimensional quantity, comprising a variable inductor having at least two partially interfacing parts, at least one of said parts being fixed and at least one of said parts being axially displaceable, each of said parts being of nearly uniform composition and cross-sectional area; said variable inductor having an inductance varying as a square function of an axial displacement of at least one of said parts; at least one capacitor connected in parallel with said variable inductor forming a resonant circuit whose period varies as a square-root function of inductance; a variable oscillator frequency-controlled by said resonant circuit, said oscillator producing an alternating current whose period varies as a linear function of said axial displacement by combination of said square function and said square-root function; means connecting a direct-current input to said variable oscillator; means taking a periodic-current output from said variable oscillator; and means receiving said periodic-current output and measuring the relative period thereof producing a proportional measure of the axial displacement of said axially displaceable part.

Claim 5

The invention defined in claim 2, wherein said at least two partially interfacing parts are a fixed coil, and a movable magnetic core.

Claim 6

The invention defined in claim 2, further comprising a compensating sleeve fixed surrounding said variable inductor, said sleeve being made of an electrically conducting material and having a contoured inside bore larger at the ends than in the center.

Claim 7

The invention defined in claim 2, further comprising a compensating sleeve fixed surrounding said variable inductor, said sleeve being made of a magnetic material and having a contoured inside bore smaller at the ends than in the center.

Claim 8

The invention defined in claim 2, wherein said at least one of said parts being fixed is a coil having fewer turns per unit length in the center than at the ends.

Claim 9

The invention defined in claim 2, wherein said at least one of said parts being fixed is a bifilar-wound coil.

Claim 10

The invention defined in claim 2, wherein said at least one of said parts being fixed is a coil, and said At least one of said parts being axially displaceable is a core of nonmagnetic material having high electrical conductivity.

Claim 11

The invention defined in claim 2, wherein said at least one of said parts being fixed is a coil, and said at least one of said parts being axially displaceable is a sleeve of nonmagnetic material having high electrical conductivity.

Claim 12

The invention defined in claim 2, wherein said at least one of said parts being fixed is a coil, and said at least one of said parts being axially displaceable is a sleeve of magnetic material.

Claim 13

The invention defined in claim 2, wherein said means receiving said periodic-current output and measuring the relative period thereof comprises a digital counter; means time-gating said digital counter on in proportion to the period of said periodic output; a second oscillator providing pulses counted by said digital counter when said counter is gated on; and a digital output means interconnected with said digital counter.

Claim 14

A transducer system for measuring a dimensional quantity, comprising a variable inductor having at least two coaxially interfacing parts, at least one of said parts being fixed and at least one of said parts being axially displaceable, each of said parts being of nearly uniform composition and cross-sectional area; said variable inductor having an inductance varying as a square function of an axial displacement of at least one of said parts; at least one capacitor connected in parallel with said variable inductor forming a resonant circuit whose period varies as a square-root function of inductance; a variable oscillator frequency-controlled by said resonant circuit, said oscillator producing an alternating current whose period varies as a linear function of said axial displacement by combination of said square function and said square-root function; means for connecting a direct-current input to said variable oscillator; means taking a periodic-current output from said variable oscillator; a digital counter; means time-gating said digital counter on in proportion to the period of said periodic output; a second oscillator providing pulses counted by said digital counter when said counter is gated on; and a digital output means interconnected with said digital counter and yielding a number variable in proportion to said axial displacement.

Claim 15

A transducer system for measuring a dimensional quantity, comprising a variable inductor having at least two coaxially interfacing parts, at least one of said parts being fixed and at least one of said parts being axially displaceable, each of said parts being of nearly uniform composition and cross-sectional area; said variable inductor having an inductance varying as a square function of an axial displacement of at least one of said parts; at least one capacitor connected in parallel with said variable inductor forming a resonant circuit whose period varies as a square-root function of inductance; a variable oscillator frequency-controlled by said resonant circuit, said oscillator producing an alternating current whose period varies as a linear function of said axial displacement by combination of said square function and said square-root function; means for connecting a direct-current input to said variable oscillator; means taking a periodic-current output from said variable oscillator; a digital counter; means time-gating said digital counter on in proportion to the period of said periodic output; a second oscillator providing pulses counted by said digital counter when said counter is gated on; and a digital output means interconnected with said digital counter and yielding a number variable in proportion to said axial displacement.

Claim 16

The invention defined in claim 12, wherein said at least one of said parts being fixed is a coil; and said at least one of said parts being axially displaceable is a core.

Claim 17

The invention defined in claim 12, wherein said at least one of said parts being fixed is a coil; and said at least one of said parts being axially displaceable is a sleeve.

Claim 18

The invention defined in claim 12, wherein said at least one of said parts being fixed is a coil having fewer turns per unit length in the center than at the ends, and wound on a core of magnetic material; and said at least one of said parts being axially displaceable is a sleeve.

Claim 19

The invention defined in claim 12, wherein said at least one of said parts being fixed is a bifilar-wound coil.

Claim 20

The invention defined in claim 12, further comprising a compensating sleeve fixed coaxially surrounding said variable inductor, said sleeve being made of an electrically conducting material and having a contoured inside bore larger at the ends than in the center.

Claim 21

The invention defined in claim 12, further comprising a compensating sleeve fixed coaxially surrounding said variable inductor, said sleeve being made of a magnetic material and having a contoured inside bore smaller at the ends than in the center.