Patent US4069710A successfully refreshed from Google Patents.
US4069710A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for the capacitative measurement of the surface level of fluid media in vessels
Assignee: Individual
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Filing: 1977-01-21
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Granted: 1978-01-24
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Expires: 1997-01-21
Abstract
Abstract Apparatus for the capacitative measurement of the surface level of a fluid medium in a vessel comprises a probe mounted to provide a capacitance between itself and the surface, the probe being connected into one of two RC-circuits, respectively connected to opposite ends of a secondary winding of a transmitter, the primary winding of which is in a resonant high-frequency generator circuit. The two RC-circuits are earthed and respectively connected through rectifiers to the inputs of a differential amplifier, the output of which provides an output signal corresponding to the capacitance between the probe and surface level. The RC-circuit associated with the probe comprises a parallel manually adjustable capacitor and a capacitance diode arranged for the remote adjustment of the RC-circuit. Where there is a substantial separation of the probe from the RC-circuits a two-core high-frequency cable is used with one core connecting the probe into the associated RC-circuit and the other core connecting an insulated point on the probe to the other RC-circuit. A simple, sensitive apparatus, unaffected by temperature variations is thereby provided.
Inventors
- 👤 Otto Treier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:00
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/26; G01F23/263
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
198 words
Apparatus for the measurement of the surface level of a fluid medium in a vessel, comprising a vessel, a high-frequency electrical generator, a high-frequency transmitter having inductively coupled primary and secondary portions, means connecting said generator and said transmitter for the supply of high frequency electric current to said primary portion, first and second terminal connectors with said secondary portion connected therebetween to provide a high-frequency induced current between said terminal connectors, a first capacitor, means earthing said first terminal connector by way of said first capacitor, a probe mounted on said vessel to provide a second capacitor providing a capacitance between said probe and fluid medium in said vessel, said capacitance depending on the surface level of fluid medium in said vessel, means earthing said second terminal connector by way of said second capacitor, rectifier means, and means connecting said rectifier means to said first and second capacitors for the rectification of alternating voltages present on said capacitors, thereby providing direct-current voltage outputs respectively from said first and second capacitors, and means having two inputs respectively connected to receive said voltage outputs and itself providing an output corresponding to said capacitance and, therefore, to said surface level.
Claim 2
Dependent Claim
198 words
Apparatus for the measurement of the surface level of a fluid medium in a vessel, comprising a vessel, a high-frequency electrical generator, a high-frequency transmitter having inductively coupled primary and secondary portions, means connecting said generator and said transmitter for the supply of high frequency electric current to said primary portion, first and second terminal connectors with said secondary portion connected therebetween to provide a high-frequency induced current between said terminal connectors, a first capacitor, means earthing said first terminal connector by way of said first capacitor, a probe mounted on said vessel to provide a second capacitor providing a capacitance between said probe and fluid medium in said vessel, said capacitance depending on the surface level of fluid medium in said vessel, means earthing said second terminal connector by way of said second capacitor, rectifier means, and means connecting said rectifier means to said first and second capacitors for the rectification of alternating voltages present on said capacitors, thereby providing direct-current voltage outputs respectively from said first and second capacitors, and means having two inputs respectively connected to receive said voltage outputs and itself providing an output corresponding to said capacitance and, therefore, to said surface level.
Claim 3
Dependent Claim
16 words
Apparatus according to claim 1, in which said means having two inputs is a differential amplifier.
Claim 4
Dependent Claim
47 words
Apparatus according to claim 2, in which said differential amplifier comprises a bistable control circuit of which one condition is present below a predetermined voltage differential value of said direct-current voltage outputs of said rectifier means and the other condition is present at and above said value.
Claim 5
Dependent Claim
29 words
Apparatus according to claim 1, comprising a further capacitor and means earthing said second terminal connector by way of said further capacitor and in parallel with said second capacitor.
Claim 6
Dependent Claim
15 words
Apparatus according to claim 14, in which said further capacitor is a manually adjustable capacitor.
Claim 7
Dependent Claim
14 words
Apparatus according to claim 4, in which said further capacitor is a capacitance diode.
Claim 8
Dependent Claim
43 words
Apparatus according to claim 4, comprising a first re-charging resistor connected between said first terminal connector and earth, in parallel with said first capacitor, and a second re-charging capacitor connected between said second terminal connector and earth, in parallel with said further capacitor.
Claim 9
Dependent Claim
42 words
Apparatus according to claim 1, in which said generator and transmitter are connected together in a resonant circuit and in which said capacitors connected to said first and second terminal connectors provide, at least partially, an oscillator capacitance for said resonant circuit.
Claim 10
Dependent Claim
40 words
Apparatus according to claim 1, comprising a two-core high-frequency cable, one said core providing said means earthing said second terminal connector, and the other said core being connected between said first terminal connector and an insulated location on said probe.
Claim 11
Dependent Claim
24 words
Apparatus according to claim 1, comprising a recharging resistor, said secondary portion of said transmitter having a centre tapping connected to said re-charging resistor.
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) | 1981-01-23 | 1981-07-25 | 1982-01-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-23 | 1985-07-25 | 1986-01-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-23 | 1989-07-25 | 1990-01-24 | $7700.00 | Window Closed / Lapsed |