Measuring and testing – Gas analysis – Moisture content or vapor pressure
Patent
1995-06-12
1997-01-28
Brock, Michael
Measuring and testing
Gas analysis
Moisture content or vapor pressure
73 2504, 73 2905, G01N 2556
Patent
active
055979530
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to measuring equipment and can be used for the measurement of gas and aerosol concentrations, in particular, water vapor in gas and aerosol mixtures as well as flow-velocity and temperature of aerosol and gas mixtures.
BACKGROUND OF THE INVENTION
Currently, known in the art is a moisture sensor (DE patent No. 3829517, cl. G01N25/56, 1989) wherein on a surface of a flat substrate made of low heat conductivity material, a tape heater in the form of meander is printed, on which an insulation layer is sprayed and on which, in turn, a moisture sensitive layer is deposited with a sensitive element inside the latter.
The prior art moisture sensor operates on the principle of cyclic conversion of a moisture sensitive layer parameter proportional to moisture of the environment, to an electric signal to be measured at the sensitive element outputs when the sensor reaches the ambient temperature. After the measurement period is finished, voltage is fed to the heater located on the substrate and separated from the moisture-sensitive layer by an insulating layer due to which a temperature of the whole moisture sensor begins to rise to the preset value, and as a result, the moisture-sensitive layer is dried; then the heating is stopped and the sensor cools down naturally, whereupon the measurement cycle is repeated.
Thus, the prior art moisture sensor has a long relaxation time (response speed), inasmuch as the heater and moisture sensitive layer are separated, which slows down a reaction of the moisture sensitive layer to ambient parameter changes.
Moreover, the prior art moisture sensor has a low efficiency due to the presence of an insulating layer between the heater and moisture sensitive layer, which leads to additional power consumption because power of the heater is additionally consumed for the heating of the insulating layer and substrate.
DISCLOSURE OF THE INVENTION
The object of the invention is to provide a moisture sensor of a new design which allows for a substantial increase in relaxation time (response speed) and efficiency.
Said object is achieved by a moisture sensor comprising a flat substrate, for example, rectangular, a moisture-sensitive layer formed by spraying, and a tape heater in a form of a broken line, for example, a meander, formed by spraying, wherein according to the present invention on a surface of said flat substrate, made of monocrystalline silicon, a silicon dioxide film, functioning as an insulation layer, is formed by thermal oxidation; windows, for example, rectangular, are etched in both faces of the silicon dioxide film, opposite each other; a tape heater is deposited on one of the faces of the flat substrate and the unetched part of the silicon dioxide film; a window, for example, rectangular, is etched in the other face of the flat substrate, said window being matched with the windows in the silicon dioxide film; a moisture-sensitive layer is further sprayed on both faces of the tape heater, located above the window in the flat substrate, said tape heater additionally functioning as a sensitive element with terminals.
The moisture sensor according to the present invention allows to reduce relaxation time (increase response speed) owing to the fact that the tape heater additionally functions as a sensitive element, i.e. an intermediate material separating the heating and sensitive elements is absent providing undelayed transmission information on environment parameters to the sensor output.
Additionally, this moisture sensor provides an efficiency improvement due to the fact that a contact between the substrate and tape heater is minimum, and there is no insulation layer between the heater and moisture sensitive layer.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained by a description of concrete embodiments of its construction with reference to the accompanying drawings, in which
FIG. 1 shows a principal view of the moisture sensor according to the invention;
FIG. 2 shows a cross-section of the moisture sensor accordin
REFERENCES:
patent: 4203087 (1980-05-01), Kovac et al.
patent: 4793181 (1988-12-01), Djorup
"Otkrytia izobretenia", N 19, 1991, VNIIPI, (Moscow), S. 174, SU, A1, 1651180 (Nauchno-issledovatelsky institut . . . ) 23 May 1991 (23 May 1991) & an English translation thereof.
Polivanov Pavel P.
Usanov Jury G.
Voronov Jury A.
Brock Michael
Usanov Jury Gennadievich
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