Patent US3874237A successfully refreshed from Google Patents.
US3874237A
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Liquid level height measuring apparatus
Assignee: National Research Council Canada
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Filing: 1973-02-15
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Granted: 1975-04-01
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Expires: 1993-02-15
Abstract
Abstract A liquid level height measuring device that is a transmission line oscillator comprising a parallel conductor transmission line positionable in the liquid whose height is to be measured and a sensor in the form of a switching device whose switching frequency is dependent only on transmission line length and thus on liquid level. The transmission line preferably includes a length of flexible coaxial cable connected in series to a rigid coaxial conductor structure with the center conductor positioned in relation to and electrically insulated from the outer conductor which has perforations over its working length for ready entry of the liquid into the space between conductors. The sensor is a two terminal bistable switching device, preferably a tunnel diode, connected to the transmission line such that a switching signal is generated whose frequency is dependent only on the transmission length.
Inventors
- 👤 Cornelis M G Zwarts
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:17
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/28; G01F23/284
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
107 words
A liquid level measuring device comprising: a. an oscillator made up of a transmission line positionable in the liquid so that the liquid surface provides a reflection causing discontinuity in said line and an electrically energized tunnel diode connected to said line and transmitting a wavefront along said line when switched from one state to the other and being switched to a second state by a reflected wavefront obtained from said line, and b. means for measuring the period or frequency of oscillation of said oscillator, said period or frequency being related to the distance from the switching device along the transmission line to the liquid surface.
Claim 2
Dependent Claim
107 words
A liquid level measuring device comprising: a. an oscillator made up of a transmission line positionable in the liquid so that the liquid surface provides a reflection causing discontinuity in said line and an electrically energized tunnel diode connected to said line and transmitting a wavefront along said line when switched from one state to the other and being switched to a second state by a reflected wavefront obtained from said line, and b. means for measuring the period or frequency of oscillation of said oscillator, said period or frequency being related to the distance from the switching device along the transmission line to the liquid surface.
Claim 3
Dependent Claim
132 words
Apparatus for measuring the surface level of conductive or high permittivity liquids comprising: a. a transmission line having first and second conductors spaced one from the other with a first end of said line adapted to be placed below the liquid surface; b. a tunnel diode connected to the second end of said line and adapted to oscillate from a first stable state, which transmits a wavefront along the line, to a second stable state when the wavefront, phase reversed and partially reflected from the liquid surface, reaches the second end, and back to the first stable state on termination of the reflected wave; and c. detecting means connected across the second end of said line and adapted to indicate the liquid level in terms of the period or frequency of oscillation.
Claim 4
Dependent Claim
132 words
Apparatus for measuring the surface level of conductive or high permittivity liquids comprising: a. a transmission line having first and second conductors spaced one from the other with a first end of said line adapted to be placed below the liquid surface; b. a tunnel diode connected to the second end of said line and adapted to oscillate from a first stable state, which transmits a wavefront along the line, to a second stable state when the wavefront, phase reversed and partially reflected from the liquid surface, reaches the second end, and back to the first stable state on termination of the reflected wave; and c. detecting means connected across the second end of said line and adapted to indicate the liquid level in terms of the period or frequency of oscillation.
Claim 5
Dependent Claim
37 words
Apparatus as in claim 2 wherein the transmission line is a rigid coaxial line made up to an inner metal conductor and a cylindrical metal outer conductor in spaced relation and electrically insulated from the inner conductor.
Claim 6
Dependent Claim
38 words
Apparatus as in claim 3 wherein the said cylindrical, metal, outer conductor contains perforations over at least some part of its operating length for ready and rapid passage of liquid into and out of the space between conductors.
Claim 7
Dependent Claim
47 words
Apparatus as in claim 2 wherein the transmission line includes a length of flexible coaxial cable electrically connected to a length of rigid coaxial line made up of an inner metal conductor and a cylindrical outer conductor in spaced reLation and electrically insulated from the inner conductor.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-31 | 1978-09-30 | 1979-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-31 | 1982-09-30 | 1983-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-31 | 1986-09-30 | 1987-04-01 | $7700.00 | Window Closed / Lapsed |