US3864974A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Capacitance probe and system for precision measurement of liquid level
Assignee: Individual
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Filing: 1972-11-27
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Granted: 1975-02-11
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Expires: 1992-11-27
Abstract
Abstract The capacitance probe consists of a vertical insulated wire stretched taut in the tank, or other container, where liquid level is to be measured. Fittings at the top and bottom conveniently and efficiently support and tighten the wire. The system comprises an oscillator which impresses a sinusoidal voltage in series with the probe, preferably through a transformer so that there are no active electronics at the probe. One end of the probe is at ground potential. A long transmission line may connect the probe to the measuring electronics. Zero and maximum references are individually calibrated by means of potentiometers. The zero signal is rectified by a precision detector, so that the zero signal follows or tracks the maximum signal automatically. The probe signal, properly amplified, also passes through a detector, and this signal and the automatic zero signal are fed to a differential amplifier and thence to a meter or control device.
Inventors
- 👤 George P Rauchwerger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 00:38
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/26; G01F23/263
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
155 words
A liquid level measuring system for use in a container comprising an oscillator having one terminal at ground potential, a capacitance probe to be immersed in the liquid to be measured, said probe having a conductor, the lower end of said conductoor being adjacent the bottom of said container, said conductor sheathed by an insulator, the other conductor of said probe comprising the liquid in said container, a transformer having one coil in series with said oscillator and being at ground potential at the opposite end and a second coil in series with said probe at one end and with a measuring circuit at the other end, said measuring circuit being remote from said probe, said transformer and said probe being located in close proximity to each other and separated from sid measuring circuit by long wires, said measuring circuit comprising a charge amplifier having its input connected at one end to said second coil.
Claim 2
Dependent Claim
155 words
A liquid level measuring system for use in a container comprising an oscillator having one terminal at ground potential, a capacitance probe to be immersed in the liquid to be measured, said probe having a conductor, the lower end of said conductoor being adjacent the bottom of said container, said conductor sheathed by an insulator, the other conductor of said probe comprising the liquid in said container, a transformer having one coil in series with said oscillator and being at ground potential at the opposite end and a second coil in series with said probe at one end and with a measuring circuit at the other end, said measuring circuit being remote from said probe, said transformer and said probe being located in close proximity to each other and separated from sid measuring circuit by long wires, said measuring circuit comprising a charge amplifier having its input connected at one end to said second coil.
Claim 3
Dependent Claim
64 words
A system according to claim 1 in which said measuring circuit further comprises a first detector having its input connected to the output of said charge amplifier, a second detector having its input connected to said oscillator, a differential amplifier having its inputs connected to the outputs of both said detectors and a display or control connected to the output of said differential amplifier.
Claim 4
Dependent Claim
77 words
A system according to claim 2 which further comprises zero adjusting means comprising a voltage divider having one end connected through a buffer amplifier to said oscillator and its opposite end connected to said first coil of said transformer and having its adjustable tap connected to said second detector, said voltage divider being adjustable so that when said liquid level in said container is zero the output for said display or control corresponds to a zero reading.
Claim 5
Dependent Claim
75 words
A system according to claim 2 which further comprises a maximum adjusting means comprising a voltage divider having one end terminal connected through a buffer amplifier to said oscillator and its opposite end terminal to ground and its center tap connected to the first coil of said transformer, said voltage divider being adjustable so that when said liquid level in said container is full, the output for said display or control corresponds to maximum reading.
Claim 6
Dependent Claim
53 words
A system according to claim 2 which comprises a pair of long coaxial cable leads, both having their shields at ground potential, one said lead connecting said oscillator and said first coil of said transformer, the other said lead connecting the input of said charge amplifier and said second coil of said transformer.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-10 | 1978-08-12 | 1979-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-10 | 1982-08-12 | 1983-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-10 | 1986-08-12 | 1987-02-11 | $7700.00 | Window Closed / Lapsed |