UA75443C2 - Method for measuring moisture content of capillary-porous material - Google Patents

Abstract

The proposed method for measuring moisture content of capillary-porous material consists in determining the dielectric permittivity of the material attwo different frequencies of the test signal, measuring dielectric loss tangent for the material at the said frequencies, determining the difference between the dielectric loss tangent values at the said frequencies, and using the data so obtained for determining the moisture content by a specified equation. The present invention provides a possibility to increase measurement accuracy by excluding the error that is caused by the instability of dielectric losses in material.

Description

Description of the invention

The invention relates to measuring equipment and can be used to determine the moisture content of 2 capillary-porous loose materials, such as grain and grain products.

There is a known method of measuring humidity by weighing five-gram portions of the material before and after drying. The moisture content of the material is determined by the difference in the mass of the wet and dry material | Skrypnyk N. N.,

Koval V. A. Handbook of tools and means of automation for quality control of agricultural production. - K.: Urozhai, 1988, p. 481. 70 The disadvantages of the method are high labor intensity, energy consumption, and a significant subjective measurement error.

For the prototype, a method of measuring the humidity of loose materials, such as grain, by measuring the dielectric constant of these materials, for example, using a circuit with a high-frequency generator, was chosen. Dielectric permeabilities are measured at two different frequencies, the ratio of these permeabilities is determined, and humidity is determined by its value (A. p. USSR Mo183471 501М27/22, 07/4/1963). 12 The disadvantage of the method is the low accuracy of humidity measurement, since dielectric permeability as a function of the measured capacity of the material depends not only on the moisture in the material, but also on the unstable dielectric losses of the material, which are not determined in this method, which leads to significant measurement errors.

The invention is based on the task of increasing the accuracy of measurements of free moisture in capillary-porous materials by additionally measuring the tangent of the dielectric loss angle at two frequencies and finding the difference in dielectric loss coefficients at these frequencies, which is proportional to the value of moisture in the material.

The problem is solved by the fact that in the method of measuring the humidity of capillary-porous materials, by measuring the dielectric constant of these materials, for example, using a circuit with a high-frequency generator c 29 at two frequencies, the tangent of the angle of dielectric losses is measured at these same frequencies, and the humidity (Ho) determined by the difference in the coefficient of dielectric loss, determined at frequencies y and 5, according to the following formula: eV AK-N.(K-K.o)- V. "More - from "82' where 8 is the proportionality coefficient; со со Ak - increase in dielectric loss coefficient;

Ku - dielectric loss coefficient at frequency y; "

Ka - dielectric loss coefficient at frequency 5; "I "1 - dielectric constant at frequency y; ой х2 - dielectric constant at frequency 2; 3o av, - the tangent of the dielectric loss angle at frequency y; - also - the tangent of the dielectric loss angle at the frequency.

In fig. 1 shows the dependences of the dielectric loss coefficient on humidity for two frequencies 7/ and 5, and x 25. Frequencies l and 2 are chosen experimentally in the region of low-frequency polarization, which is typical for free moisture. It can be seen from the graphs that the coefficient of dielectric loss of bound moisture does not depend on the frequency. c In fig. 2 shows the dependence of the increase in the dielectric loss coefficient on humidity, from which it can be seen that the increase in the dielectric loss coefficient changes proportionally with the change in free moisture in the capillary-porous material.

The coefficient of dielectric loss 49 Ka d5 is a collective characteristic of the material, which takes into account the presence of dielectric loss and moisture in (9) the material under study. The increase in the dielectric loss coefficient is the difference between the dielectric loss coefficients at frequencies 7 and 5, and "5,

AK o-K,-Ka sht Yid64-53 53

Its 50 Thus, measuring the tangent of the angle of dielectric losses at frequencies 7 and 5" allows to take into account the influence on the result of measurements of unstable dielectric losses and thereby increase the accuracy of measuring the humidity of capillary-porous materials.

Claims (1)

The formula of the invention is a method of measuring the humidity of capillary-porous materials by measuring the value of the dielectric permeability of the material at two frequencies, for example, using a circuit with a high-frequency generator, which differs in that at the same frequencies the tangent of the dielectric loss angle is additionally measured, and 60, the moisture content of the material is determined by the difference in the values of the dielectric loss coefficient at frequencies y and b, under conditions 4-5, by the expression between zhV.AK VC. -K.)1-8 (EE, 1464 -5a3 4637), where B is the proportionality coefficient; 65 AK - increase in dielectric loss coefficient; Ku - dielectric loss coefficient at its frequency; Ka. - the coefficient of dielectric loss at the frequency i"; E4 - Relative dielectric constant at frequency y;; ha - Relative dielectric constant at frequency 1"; db - the tangent of the dielectric loss angle at frequency y; 45. - the tangent of the dielectric loss angle at frequency 5. s 6) (ze) « « IS) and - - with . and? -I 1 sh» sh» syu» ime) 60 b5