SU1372223A1 - Dew point hygrometer - Google Patents

Description

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The invention relates to the field of plaometry and can be used to measure the humidity of atmospheric air and gases of industrial installations.

The purpose of the invention is to improve the accuracy and reliability of measurements.

The drawing shows a schematic diagram of the proposed device.

The hygrometer contains a dual beam illuminator 1, a temperature sensor 2 applied to the surface of the element 3 of multiple impaired total internal reflection (ATRM), photo receivers A. The device also includes an electronic control and dew point indication system including an electronic switch b, trigger

6, the synchronizer 7, the dew point temperature indicator 8 and the controlled power supply unit 9. The ATR element is in thermal contact with the cooler 10.

The dew point hygrometer functions as follows.

After turning on the cooler 10, an ATRM element 3 is cooled, through which, alternately according to the command given by the synchronizer 7, light beams from the illuminator 1 pass. When the temperature (measured by sensor 2) corresponding to the dew point temperature reaches The ATRM condensate falls out, which immediately affects the intensity of the light that passes through the ATRM element (the moisture does not affect the reference light beam), drastically changes the ratio of the reference light fluxes and the reading light. o rays. This change is detected by trigger 6, which receives a signal in differential form from an electronic switch 5, which, in turn, receives a signal from a photodetector 4. The synchronization of the electronic switch with the sequence of switching on the LEDs is performed. The trigger 6 issues a command to the temperature indicator 8 where the dew point temperature is fixed at a given time, and the second command feeds the block

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starts to heat until the condensate on the surface evaporates, after which the trigger returns to its original state and the measurement process is repeated.

The device does not require calibration operations on the reference humidity before each measurement event, since the humidity of gases is determined by calculation or graphically from the dew point temperature measured by a temperature sensor deposited on the surface of the ATR element.

The introduction of selective radiation in the field of characteristic water absorption into the reference method for determining moisture by the dew point significantly improves the accuracy and reliability of the measurement, since the reading beam only reacts to the presence of moisture on the surface of the ATR element and does not react to impurities that can condense or leave gas while cooling this surface. This allows the proposed device to measure the humidity of not only air, but also industrial gases and their mixtures.

The lighter can be made with wavelengths of 1.94 microns, which corresponds to the characteristic absorption of water, and with 1.77 microns. Wavelength 7 is related to the refractive index of the material of the ATRM element by the ratio given in the claims. This ratio makes it possible to determine the angles of input and output of radiation into the ATR element, at which optimum interaction of the radiation with a film of water on the surface of the ATR element is ensured. For example, for optical glass of the EEC1 mark, the radiation transmission band is in the wavelength range from 1.2 to 2.1 µm, where there is a maximum of the characteristic absorption of water. At the same time, the angle of input and output of radiation into the ATR element is determined from the expression B given by the expression, where S is the depth of penetration of the reading beam into the dew film on the surface of the ATR element being equal to 0.5-1.0 µm, which ensures

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Claims (1)

DEW POINT HYGROMETER, containing a illuminator optically coupled to a photodetector through a multiple impaired total internal reflection (MNIPO) element with a temperature sensor deposited on its surface, a cooler in thermal contact with the MNIPO element, as well as an electronic control and indication system for the dew point with a lighter, a photodetector, a temperature sensor and a cooler, it is important that, in order to increase the accuracy and reliability of measurement, the lighter is made in the form of a two-beam optical system with a reading beam with a wavelength (λ, and a reference beam with a wavelength, the wavelength of '3 ₁ corresponds to the wavelength of the characteristic absorption of water, and the INME element is made of a material with selective transparency in the region of the selected wavelengths l ft such that the relation ΔΆ -? Ά, wherein the radiation input and output angle svya- ATR element coupled to a wavelength hours scanning beam and the refractive index of material η ratio ATR element • ^2/1 \ 2. о Г sin о + п, where о - estimated ¹ 4п о depth of penetration of the reading beam into the dew film on the surface of the MNVPO element. SU „„ 1372223