RU2174678C1 - Process estimating moisture content and density - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: invention refers to equipment determining moisture content and density of various substances, specifically, loose substances, agricultural crops, products of their processing and grounds. For realization of process there are used two converters of physical-chemical properties to electric signals with two pairs of electrodes. First electrodes are electrically common, second electrode of second converter on side of first electrode is covered by layer of dielectric matter. Examined substance is placed into converters. Temperature of medium and examined substance and electric signals across second electrodes are measured. Moisture content and density are computed by results of measurements with due account of calibration tests. Process can also be employed in wood working, chemical and construction industries. EFFECT: timely and simultaneous estimation of moisture content and density in field and under stationary conditions. 2 dwg, 1 tbl

Description

 The method relates to measuring technique and can be used to determine the moisture and density of various substances: including bulk substances such as grain, flour, soil; solids like wood; liquid and gaseous substances.

 A known method for determining the moisture content of grain. GOST 13586.5-93. Methods for determining the moisture content of grain. To determine the humidity in this way, a thermogravimetric kit is used, including a drying cabinet and scales. To determine the moisture, the substance is ground, weighed, dried, again weighed, the difference in weights is determined before drying and after drying, and absolute humidity is determined from it.

 The disadvantages of using the known method is that they use an expensive kit, considerable time is required for the analysis to take up to two hours. Apply only in stationary conditions.

 A known method for determining the density of substances, in particular grains GOST 10840-64. Here, the grain is placed in a container with a known volume and constant compaction, weighed, and the density (nature) is determined.

 Known methods for determining humidity and density do not allow simultaneously in one process of the analysis to determine the humidity and density, to perform rapid analyzes in portable conditions.

 A device for measuring the moisture content of bulk substances is known - RF patent N 2130606, publ. 05/20/99 in the "Bulletin of inventions and discoveries", N 14. The device contains a housing, a receiver - a moisture converter, a sealant, a measuring circuit, and the humidity converter is made in the form of a rectangular container of dielectric material, bounded on two sides by external flat electrodes, divided by a common electrode in parallel with two others into two equal sections, and one of them is divided into two sections, the second and third, while the third section is filled with a material with dielectric constant the dielectric constant of the substances studied for humidity, in addition, the common electrode is installed below the top of the container, and the external electrodes are smaller than the dimensions of the walls of the container, installed at its level and removed from the bottom and side surfaces of the container, the sealant is installed above the receiver with the possibility of releasing the receiver window, wherein the measuring electric circuit includes a series-connected generator, a bridge circuit to which the electrodes of the humidity transducer are connected, differential amplification s with rectifying amplifier with variable displacement, which is connected to the output node of the signal processing level, the registrar.

 This device is used for operational measurements in portable conditions. Use only for determination of humidity. Significant differences of the known device, such as the separation of the receiver into three sections, allow you to determine humidity and density at the same time. Density measurement is not provided.

 The aim of the present invention is the simultaneous operational determination of humidity and density in portable and stationary conditions.

и

(1)
где E - влажность исследуемого вещества;
K₁ и K₂ - тарировочные коэффициенты;
A и B, A₀ и B₀ - результаты измерения электрического сигнала с исследуемым веществом и базовым или эталонным образцом в первом и втором преобразователях;
E_T - поправка за температуру;
P - плотность исследуемого вещества;
P₀ - плотность базового вещества или эталонного образца;
P_T,E - поправка за температуру и влажность.This goal is achieved by the fact that when using the method, two transducers are used for the physicochemical properties of the substance - an electrical signal with two pairs of electrodes, of which the first electrodes are electrically shared, the second electrode of the second transducer on the side of the first electrode is closed with a layer of dielectric substance, the test substance is placed between pairs of electrodes, measure the temperature of the medium and substances, measure the electrical signals at the second electrodes, calculate taking into account calibration measurements humidity and density of the substance according to the following formulas:

and

(1)
where E is the moisture content of the test substance;
K ₁ and K ₂ - calibration factors;
A and B, A ₀ and B ₀ are the results of measuring an electrical signal with the test substance and a base or reference sample in the first and second transducers;
E _T - correction for temperature;
P is the density of the test substance;
P ₀ is the density of the base substance or reference sample;
P _{T, E} - correction for temperature and humidity.

 Using two converters allows you to use the differences in the physical dependencies of the parameters of the electrical signals. The parameters of the electrical signals at the second electrodes depend on the degree of moisture and density of the investigated substances. In this case, the effect of humidity in the first converter is more noticeable, because here, the influence of dielectric losses is affected more due to the proximity of the substance to the second electrode. In the second converter, the influence of the density of the test substance is more noticeable. The dielectric constant depends on the density. The effect of dielectric loss is sharply reduced, because the substance is distant from the second electrode. At the electrically common electrode, the dielectric losses in both converters are the same.

 The logical conclusions and the results of numerous experiments confirm the validity of the above formulas.

 In FIG. 1 shows graphs of the dependence of the parameter of the electric signal in relative units on the moisture and density of the investigated substances. The solid line shows this dependence in the first converter, the dotted line shows the dependence of the electric signal in the second converter with a layer of dielectric substance.

 In FIG. 2 shows a diagram of a device for implementing the method. A device for implementing the method includes: 1 - a first transducer, 2 - a second transducer, 3 - a common electrode, 4 and 5 - second electrodes in the transducers, 6 - a dielectric layer, 7 - a circuit for primary processing of electrical signals, 8 - temperature sensor, 9 - three-channel amplification circuit, 10 - microcontroller, 11 - indicator.

 The device includes two transducers 1 and 2. The design with a common electrode 3 allows you to simultaneously fill both transducers with the same seal. The layer of dielectric substance 6 can be any dielectric from air to a heavy dielectric, like glass, the optimal choice depends on the physicochemical properties of the studied substances. In the role of the primary processing unit of the electrical signals 7 use a bridge circuit. The three-channel amplification circuit of the electrical signals 9 coordinates the output resistances of the bridge circuit 7 and the input resistances of the microcontroller 10, amplifies the electrical signals taken from the electrodes 4 and 5 and the temperature sensor 8. The microcontroller 10 with built-in analog-to-digital converter, arithmetic-logic device, memory and The program introduced solves the above algorithms (1), performs logical operations, and controls the operation of the indicator. The results of determining the humidity and density are displayed on the screen of the indicator 11. These results are corrected for the difference between the temperatures of the calibration measurements and the actual ones, the result of the determination of the density is additionally corrected for the measured humidity.

Calibration measurements were made with the manufactured device. Using these measurements, calibration coefficients K ₁ and K _{2 are} determined. To do this, use a set of substances with known moisture and density, which are measured by known methods.

The procedure for determining humidity and density is as follows. The test substance is placed in converters 1 and 2. From the electrodes 4 and 5, the electric signals of a certain frequency and amplitude generated by the generator in the electric circuit are supplied to the bridge circuit 7, then each is amplified by an amplifier 9 and then processed in the microcontroller 10. Here the moisture determination algorithms are solved and density (1) taking into account calibration coefficients K ₁ and K ₂ , which are entered into the memory of the microcontroller. These results are corrected for the difference between the actual and calibration temperatures, which allows the temperature sensor 8 and communication sensor 8 - amplifier 9 - microcontroller 10 to be connected, the density is additionally corrected for the humidity obtained.

 The table shows the results of the definitions for crops in comparison with the actual humidity and density, measured by known methods. As the results show, the accuracy of determining moisture is not worse than 0.5%. Deviations in densities are somewhat larger. Here in research and development less experience is gained.

Claims (1)

A method for determining humidity and density, characterized in that two transducers use the physicochemical properties of the substance — an electrical signal with two pairs of electrodes, of which the first electrodes are electrically shared, the second electrode of the second transducer is closed on the side of the first electrode with a layer of dielectric substance, the test substance is placed between pairs of electrodes, measure the temperature of the medium and substances, measure the electrical signals at the second electrodes, calculate taking into account calibration measurements th humidity and density of the material according to the formulas

and

where E is the moisture content of the test substance;
K ₁ and K ₂ - calibration factors;
A and B, A ₀ and B ₀ are the results of the measurement of an electrical signal with the test substance and a base or reference sample in the first and second transducers;
E _T - correction for temperature;
P is the density of the test substance;
P ₀ is the density of the base substance or reference sample;
P _{T, E} - correction for temperature and humidity.

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