Patent US4890494A successfully refreshed from Google Patents.
US4890494A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Atmospheric sensor
Assignee: BAE Systems Electronics Ltd
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Filing: 1988-05-17
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Granted: 1990-01-02
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Expires: 2008-05-17
Abstract
Abstract A device for measuring the liquid content of a gas, as for example measuring the liquid water content in the atmosphere. The device employs a probe fabricated in part from a material which is thermally self-stabilizing and which preferably has a positive temperature coefficient. In use the probe is electrically heated and disposed in a flowing gas or is adapted for movement through a static gas so that droplets of liquid are deposited on the surface of the probe. Means is provided for detecting a change in the electrical resistance of the probe in response to a change in the heat loss rate due to the integrated evaporation of droplets of liquid from the surface of the probe. The temperature of the gas, the degree of relative movement between the probe and the gas, and the gas pressure are also sensed so that when their measurements are processed with a measurement dependent on the change in the electrical resistance of the probe a measurement is obtained of the liquid droplet content in the gas. A particular application for the device is that of measuring the liquid water contents in the air flowing around helicopters and other aircraft, so that the crew can be given warning when they are flying into icing conditions.
Inventors
- 👤 Paul C. Osbond
- 👤 Roger W. Whatmore
- 👤 John P. Auton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 09:45
CPC Classifications
G; G01; G01N; G01N25/00; G01N25/56; G01N27/00; G01N27/02; G01N27/04; G01N27/14; G01N27/18
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
180 words
A device for measuring a liquid content of a gas, the device including a probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, means for heating the probe to a required temperature, means for detecting a change in the electrical resistance of the probe, in response to a change in the heat loss rate due to the integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, means for maintaining the temperature of the probe substantially constant during operation whereby the change in the electrical resistance indicates a variation in power used to maintain the temperature of the probe substantially constant, and means for processing the variation of power for determining the liquid content of the gas.
Claim 2
Independent Claim
180 words
A device for measuring a liquid content of a gas, the device including a probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, means for heating the probe to a required temperature, means for detecting a change in the electrical resistance of the probe, in response to a change in the heat loss rate due to the integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, means for maintaining the temperature of the probe substantially constant during operation whereby the change in the electrical resistance indicates a variation in power used to maintain the temperature of the probe substantially constant, and means for processing the variation of power for determining the liquid content of the gas.
Claim 3
Dependent Claim
77 words
A device according to claim 1 wherein the ceramic material has a positive temperature coefficient of resistance, and the device further comprises means for measuring a current drawn by the probe to determine the change in electrical resistance of the probe, means for measuring relative movement between the probe and the gas, the temperature of the gas and gas pressure, and means for processing the measurements to obtain a measurement of the liquid content of the gas.
Claim 4
Dependent Claim
85 words
A device according to claim 2 wherein the electrical resistivity P of the ceramic material at a temperature θ above the Curie temperature θ N is given by the equation: P=P.sub.o exp (n.sub.2 (θ-θ.sub.N) where n 2 , known as the temperature coefficient, defines the fractional rise in resistivity per degree centigrade above the Curie temperature θ N , and wherein the ceramic material is chosen to have a Curie temperature above 50° C. and the temperature coefficient is greater than 0.1020 C. -1 .
Claim 5
Dependent Claim
20 words
A device according to claim 3 wherein the probe material comprises a doped barium titanate (BaTiO 3 ) semiconductor ceramic.
Claim 6
Dependent Claim
21 words
A device according to claim 1 wherein at least a portion of the probe ceramic material is substantially cylindrical in configuration.
Claim 7
Dependent Claim
22 words
A device according to claim 5 wherein the probe structure comprises at least one ceramic toroid manufactured from the thermally self-stabilising material.
Claim 8
Dependent Claim
71 words
A device according to claim 1 wherein the probe ceramic material has a negative temperature coefficient of resistance and the device further comprises means for measuring a potential difference across the probe while a current is maintained constant, means for measuring relative movement between the probe and the gas, means for measuring gas pressure, and means for processing the measurements to obtain a measurement of the liquid content of the gas.
Claim 9
Independent Claim
148 words
A device for measuring a liquid content of a gas including a probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, and means for detecting a change in the electrical resistance of the probe, in response to a change in the heat loss rate due to the integrated evaporation of droplets of liquid from the surface of the ceramic material, the probe including a plurality of substantially cylindrical ceramic toroids of the thermally self-stabilising material, wired electrically in parallel and stacked on top of one another to form a cylinder.
Claim 10
Independent Claim
148 words
A device for measuring a liquid content of a gas including a probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, and means for detecting a change in the electrical resistance of the probe, in response to a change in the heat loss rate due to the integrated evaporation of droplets of liquid from the surface of the ceramic material, the probe including a plurality of substantially cylindrical ceramic toroids of the thermally self-stabilising material, wired electrically in parallel and stacked on top of one another to form a cylinder.
Claim 11
Independent Claim
163 words
A device for measuring a liquid content of a gas including a probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, and means for detecting a change in the electrical resistance of the probe in response to a change in the heat loss rate due to the integrated evaporation of droplets of liquid from the surface of the ceramic material, the probe including a plurality of substantially cylindrical ceramic toroids of the thermally self-stabilising material wired electrically in parallel, and the probe further including interleaving electrically conductive shims between said toroids, said toroids and interleaving shims being stacked on top of one another to form a cylinder.
Claim 12
Independent Claim
163 words
A device for measuring a liquid content of a gas including a probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, and means for detecting a change in the electrical resistance of the probe in response to a change in the heat loss rate due to the integrated evaporation of droplets of liquid from the surface of the ceramic material, the probe including a plurality of substantially cylindrical ceramic toroids of the thermally self-stabilising material wired electrically in parallel, and the probe further including interleaving electrically conductive shims between said toroids, said toroids and interleaving shims being stacked on top of one another to form a cylinder.
Claim 13
Dependent Claim
53 words
A device according to claim 9, wherein the shims are shaped to allow two electrically conductive elements to extend through the central portion of the stack, each said element making electrical contact with a respective major face of each toroid, the major faces of the toroids being coated with an electrically conductive material.
Claim 14
Independent Claim
208 words
A device for measuring a liquid content of a gas, the device including a probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having a positive temperature coefficient of resistance, an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, means for heating the probe to a required temperature, means for detecting a change in the electrical resistance of the probe, in response to a change in the heat loss rate due to the integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, means for maintaining the temperature of the probe substantially constant during operation whereby the change in the electrical resistance indicates a variation in power used to maintain the temperature of the probe substantially constant, means for measuring relative movement between the probe and the gas, the temperature of the gas and gas pressure, and means for processing the variation of power and the measurements for determining the liquid content of the gas.
Claim 15
Independent Claim
208 words
A device for measuring a liquid content of a gas, the device including a probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having a positive temperature coefficient of resistance, an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, means for heating the probe to a required temperature, means for detecting a change in the electrical resistance of the probe, in response to a change in the heat loss rate due to the integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, means for maintaining the temperature of the probe substantially constant during operation whereby the change in the electrical resistance indicates a variation in power used to maintain the temperature of the probe substantially constant, means for measuring relative movement between the probe and the gas, the temperature of the gas and gas pressure, and means for processing the variation of power and the measurements for determining the liquid content of the gas.
Claim 16
Dependent Claim
94 words
A probe for use in a device for measuring a liquid content of a gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, and the ceramic material having a positive temperature coefficient of resistance.
Claim 17
Dependent Claim
94 words
A probe for use in a device for measuring a liquid content of a gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, and the ceramic material having a positive temperature coefficient of resistance.
Claim 18
Dependent Claim
121 words
A probe for use in a device for measuring a liquid content of a gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, the probe having a substantially cylindrical shape, and the probe ceramic material also having a positive temperature coefficient of resistance and being formed in the shape of a toroid having a wall thickness of at least 0.2 mm.
Claim 19
Dependent Claim
121 words
A probe for use in a device for measuring a liquid content of a gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, the probe having a substantially cylindrical shape, and the probe ceramic material also having a positive temperature coefficient of resistance and being formed in the shape of a toroid having a wall thickness of at least 0.2 mm.
Claim 20
Dependent Claim
121 words
A probe for use in a device for measuring a liquid content of a gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic and a positive temperature coefficient of resistance, the probe having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, the probe also having a substantially cylindrical shape and having an operating temperature range of between approximately 65° C. and 75° C., and the material being a ceramic of semiconducting Barium Strontium Titanate.
Claim 21
Dependent Claim
121 words
A probe for use in a device for measuring a liquid content of a gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic and a positive temperature coefficient of resistance, the probe having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, the probe also having a substantially cylindrical shape and having an operating temperature range of between approximately 65° C. and 75° C., and the material being a ceramic of semiconducting Barium Strontium Titanate.
Claim 22
Dependent Claim
168 words
A probe for use in a device for measuring a liquid content of a gas, the probe comprising a sensor including a stack of a plurality of toroids of a ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material forming the toroids also having a positive temperature coefficient of resistance, and having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, a plurality of interleaving electrically conductive shims between adjacent pairs of toroids, electrically conductive elements extending through a central portion of the stack of toroids and interleaving shims with each said element making electrical contact with an electrically conductive material on a respective major face of each toroid, and a plastic coating on surface portions of the probe to protect the probe from the environment.
Claim 23
Dependent Claim
168 words
A probe for use in a device for measuring a liquid content of a gas, the probe comprising a sensor including a stack of a plurality of toroids of a ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, the probe ceramic material forming the toroids also having a positive temperature coefficient of resistance, and having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, a plurality of interleaving electrically conductive shims between adjacent pairs of toroids, electrically conductive elements extending through a central portion of the stack of toroids and interleaving shims with each said element making electrical contact with an electrically conductive material on a respective major face of each toroid, and a plastic coating on surface portions of the probe to protect the probe from the environment.
Claim 24
Independent Claim
171 words
A method of measuring a liquid content of a gas including the steps of measuring relative velocity between a probe and the gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, and the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, measuring temperature of the gas, measuring pressure of the gas, detecting a change in the electrical resistance of the probe, in response to a change in the heat loss rate due to the integrated evaporation of liquid droplets in said gas from the surface of the thermally self-stabilising ceramic material, providing a measurement dependent on the change in the electrical resistance of the probe, and processing the measurement to obtain a measurement of the liquid content of the gas.
Claim 25
Independent Claim
171 words
A method of measuring a liquid content of a gas including the steps of measuring relative velocity between a probe and the gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, and the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, measuring temperature of the gas, measuring pressure of the gas, detecting a change in the electrical resistance of the probe, in response to a change in the heat loss rate due to the integrated evaporation of liquid droplets in said gas from the surface of the thermally self-stabilising ceramic material, providing a measurement dependent on the change in the electrical resistance of the probe, and processing the measurement to obtain a measurement of the liquid content of the gas.
Claim 26
Dependent Claim
25 words
A method of measuring the liquid content of a gas according to claim 16 the gas is substantially air and the liquid is substantially water.
Claim 27
Dependent Claim
22 words
A method of measuring the liquid content of a gas according to claim 16 wherein the probe moves through substantially static gas.
Claim 28
Dependent Claim
42 words
A method of measuring the liquid content of a gas according to claim 15 in the probe is mounted in an air/fuel mixture stream from an internal combustion engine carburetor so as to monitor the quantity of fuel supplied by the carburetor.
Claim 29
Independent Claim
204 words
A method of measuring a liquid content of a gas including the steps of measuring relative velocity between a probe and the gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, and the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, measuring temperature of the gas, measuring pressure of the gas, detecting a change in the electrical resistance of the probe in response to a change in the heat loss rate due to the integrated evaporation of droplets of liquid from the surface of the thermally self-stabilising ceramic material, providing a measurement dependent on the change in the electrical resistance of the probe, and processing the measurement to obtain a measurement of the liquid content of the gas, wherein the temperature of the probe is maintained substantially constant and the measurement provided to measure the liquid content of the gas is the power dissipated to maintain the temperature of the probe substantially constant.
Claim 30
Independent Claim
204 words
A method of measuring a liquid content of a gas including the steps of measuring relative velocity between a probe and the gas, the probe comprising a sensor formed by ceramic material which is thermally self-stabilising because it has a known resistance/temperature characteristic, and the probe ceramic material having an electrical resistance and a heat loss rate at a surface of the ceramic material, the electrical resistance changing in response to the heat loss rate resulting from integrated evaporation of liquid droplets in said gas from the surface of the ceramic material, measuring temperature of the gas, measuring pressure of the gas, detecting a change in the electrical resistance of the probe in response to a change in the heat loss rate due to the integrated evaporation of droplets of liquid from the surface of the thermally self-stabilising ceramic material, providing a measurement dependent on the change in the electrical resistance of the probe, and processing the measurement to obtain a measurement of the liquid content of the gas, wherein the temperature of the probe is maintained substantially constant and the measurement provided to measure the liquid content of the gas is the power dissipated to maintain the temperature of the probe substantially constant.
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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) | 1993-01-01 | 1993-07-03 | 1994-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-01 | 1997-07-03 | 1998-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-01 | 2001-07-03 | 2002-01-02 | $7700.00 | Window Closed / Lapsed |