SU1133530A1 - Device for measuring gas humidity - Google Patents

Abstract

A device for measuring the moisture content of gases, containing a current meter connected to a current source and a sensing element in the form of a film with electrodes, which is similar to that in, c. In order to expand the measurement range, the film is made of polydimethylsiloxane rubber reinforced with cambric. (L with co od od sp oo

Description

f The invention relates to an analytical technique and can be used in the development of moisture meters. A device for measuring humidity is known, which contains devices that allow the recording of the mass velocity of a gas and the specific mass. thermal energy of the gas sample under investigation. The absolute humidity of a gas is determined as a function of four measured values: the flow rate of the gas under investigation, the gas temperature before and after changing its specific thermal energy and the limit of variation of this energy during the measurement process and. The disadvantages of this device are considerable complexity and relatively long analysis time. The closest technical solution to the invention is a device for measuring the moisture content of gases, which contains a current meter connected to a current source and a sensing element in the form of a film from an electrode and an element. Between the electrodes. A film partially hydrated with phosphorus pentoxide, which has a very good drying capacity, was applied. The analyzed gas is continuously passed through the sensitive element, and the consumption of gas per square meter is kept strictly constant. The geometrical dimensions of the element and the gas velocity should be such that moisture is almost completely removed from the gas. The absorbed moisture, combined with the substance of the film, forms a concentrated solvent of forsforic acid with a rather high specific conductivity. Under the influence of a current source, water is decomposed into oxygen and hydrogen, which is carried away by the flow of the analyzed gas. In the established mode, the amount of water absorbed and decomposed per unit time is equal in accordance with the Farad's law, and the current is a measure of the concentration of moisture in the analyzed gas AND. A disadvantage of the known device is that in the analyzed gas there should not be an impurity, an alkaline reaction. ammonia or amine impurities leading to rapid loss of sensitive elements. Metaphosphoric i 02 acid, which forms the film of the element, is the initiator of the polymerization reaction, in connection with which the analysis of the moisture content of a gas containing impurities of easily polymerizing components (such as diene hydrocarbons) is largely difficult. Impurities of alcohol vapors in the analyzed gas can lead to significant distortions of the indications, since the alcohols hydrolyze to phosphorus pentoxide to form water. This device only allows humidity measurements in the range from I to 5000 ppm, higher values of humidity lead to a drastic reduction in the service life of the sensing element. The aim of the invention is to extend the measurement range. This goal is achieved by the fact that, in a device for measuring the humidity of gases, which contain a current meter and sensing element connected to a current source in the form of a film with electrodes, the film is made of polydimethylsiloxane rubber reinforced with cambric. At 4wr. 1 shows a diagram of the proposed device; cha figs. 2 - the same, another option; in fig. 3 is a plot of Ig surface resistance between the electrodes and relative air humidity. A device for measuring the humidity of gases contains a meter 2 connected to a current source 1 and a sensing element in the form of a film 3 with electrodes 4. The film 3 is made of polydimethylsiloxane rubber reinforced with cambric. The electrodes 4 can be located between the film 3 and the moisture-proof fluoroplastic film 5. The device works by following this method. Under the action of an electric field between the electrodes 4, a current flows, KOT0111J is detected by a current meter 2. The magnitude of the current between the electrodes is determined by the surface resistance of the film 3 of Fig. 1) or the volume resistance (Fig. 2J. The surface or volume resistance of the film 3 depends on its humidity, which, in turn, is determined by the humidity of the surrounding environment. Thus takes place is functional

3

connection between the resistance of the film 3 (surface or bulk) and the humidity of the environment. The reading of current meter 2 is a quantitative measure of the humidity of the environment.

The proposed device was manufactured and tested. A strip of polydimethylsiloxane rubber with the size of zohbO mm, reinforced with cambric, was used as a sensitive film. Electrodes 60 mm long were connected to the film with petroleum jelly. The distance between them is 3 mm. The film 3 on the side where the electrodes are attached, in one case, shattered with a fluoroplastic film, in the other - with a strip of polydimethylsiloxane rubber SKG brand, reinforced with cambric.

A DC voltage regulator with a voltage from 0 to 400 B and accuracy of maintenance below 0.1% was used as a current source, and a current meter with a measuring range from 2-10 to 210 A and the basic error i was used to measure the current. . 1.5%. For measuring resistances in the range from 10 to 10 ohms, for example,

100 V. Air humidity was measured above the surface of saturated salt solutions, creating a certain vapor pressure. The minimum air humidity was achieved using calcium chloride, and the resistance of the film at this humidity was considered initial.

A dependency graph was obtained

resistance from relative air humidity (Fig. 3). As seen from the graph, a change in relative humidity from 0 to 100% leads to a change in resistance more,

than by 10. Since the sensitivity is characterized by the ratio of the output signal to the input measured parameter, it can be concluded that the device has a high and constant sensitivity in the range of humidity from 0 to 100%. Moreover, the measurement accuracy is limited by the accuracy of current measurement.

The proposed device will find wide application in technological processes and scientific research due to the fact that it provides measurement of humidity in a wide range, has a low cost and is easy to use.

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Claims (1)

DEVICE FOR MEASURING HUMIDITY OF GASES, comprising a current meter connected to a current source and a sensing element in the form of a film with electrodes, characterized in that, in order to expand the measurement range, the film is made of polydimethyl · siloxane rubber reinforced with batiste. FIG. 1 1 1133530 2