RU2641715C1 - Microwave device for soil moisture measuring - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention can be used in agriculture to study physical and mechanical properties of soil, in particular soil moisture. In the housing (1) of the microwave device, the power unit of the radiator (2) is placed, the microwave radiator (3) contains a resonator chamber (4) and is connected through a dielectric membrane (5) to the working chamber (7), forming a hermetic waveguide connecting with a microwave detector (8) measuring the intensity of the microwave radiation passed through the soil sample being tested. In this case, a test sample of soil enclosed in a dielectric tank (6) is installed in the working chamber (7) via the access window (11). The microwave detector (8) is connected via a data processing unit (9) to the soil moisture indication panel (10). The device is controlled by the radiator control panel (12) installed on the housing (1). The device is equipped with a global positioning module (13), which determines the coordinates of the moisture measurement points, which is connected to the data processing unit (9) and is installed in the housing. The data processing unit (9) receives signals from the microwave detector (8), the global positioning module (13), and outputs the results to the soil moisture indication panel (10). The increase in the reliability and accuracy of the moisture measurement results is a technical result of the invention.

EFFECT: device allows obtaining measurement results in relation to the coordinates of the sampling points of the soil, the device is universal for working with any types and compositions of soils.

3 cl, 2 dwg

Description

The invention relates to measuring equipment and can be used in agriculture to study the physico-mechanical properties of the soil, in particular soil moisture.

Traditional methods of measuring the moisture content of a material (including soil) by drying and weighing the samples are laborious, time consuming and do not allow mass measurements.

For example, it is known device microwave moisture meter LMA-200PM [1].

The microwave moisture meter is specially designed for the rapid determination of the moisture content of liquid, pasty substances, aqueous and non-aqueous suspensions, with a high moisture content from 8% to 100%. This moisture meter is also applicable for measuring soil moisture. The principle of operation of the moisture meter is based on dehydration (drying) of the measurement object under the influence of microwave radiation, with automatic weighing during the drying process and indication of the measurement result.

The disadvantage of this moisture meter is the length of the measurement process, which makes it impossible to mass measurements to ensure the mapping of soil moisture in the field.

Drying of soil samples also requires high energy costs, which cannot be provided in the field.

Another disadvantage is that this device does not have a global positioning module for GLONASS or GPS systems, which makes it impossible to determine the coordinates of sampling points for measuring moisture and mapping soil moisture in the field.

Thus, the use of this moisture meter for mass measurement of soil moisture in the field is impossible.

A device is known - microwave moisture meter MW 1000 [2].

The MW 1000 mobile microwave moisture measuring instrument is intended for use in laboratories and in production for the rapid determination of moisture in materials in the food (including animal feed), chemical, woodworking, paper and pharmaceutical industries. The MW 1000 is also used in the manufacture of building materials. The MW 1000 measurement method makes it possible to quickly and accurately measure moisture by simply applying a planar sensor to the material. In this case, the MW 1000 determines the total humidity regardless of the density of the material.

This moisture meter has a microwave emitting device and a receiving sensor. The device can be used to measure soil moisture.

The disadvantage of this moisture meter is the low reliability and accuracy of measurements of soil moisture due to the characteristics of the measuring circuit. The measuring circuit of the device is performed in two versions: either in the form of a planar sensor, or in the form of a probe.

When using a planar sensor, it cannot be firmly attached to the soil. Also, the emitting device and the receiving part of the planar sensor are an open circuit. Part of the electromagnetic energy is dissipated into the surrounding space, which reduces the accuracy of the measurement.

Using a measuring probe is more suitable for measuring soil moisture. However, the measuring circuit of the probe is also open (in order to accelerate the measurement process and reduce labor costs).

This device is mobile and can be used in the field, however, these shortcomings lead to a decrease in the accuracy and reliability of the measurement results.

The disadvantage is that this device, like the previous one, does not have a global positioning module, which makes it impossible to determine the coordinates of moisture measurement points and map soil moisture in the field.

The closest in combination of features is a known method and device for continuous measurement of moisture content of a granular product [3].

The method and device allow the measurement of moisture content in bulk products, in particular in the components of food production and fodder, in a measuring channel with a sensitive element for microwaves. This method and device are applicable for measuring soil moisture.

According to this method, the conductive properties of the sensitive element (detector) filled with the bulk product are measured, and according to the obtained data, humidity is determined taking into account the measured temperature and bulk density. A rod located across the flow of bulk product is used as a sensing element.

The disadvantage of this device is the low reliability of the measurements, because between the transmitting (emitter) and the sensing element (antenna) there is no sealed resonator channel. Therefore, part of the electromagnetic energy is scattered into the surrounding space, and part is absorbed by the walls of the channel through which the measured material passes. The magnitude of these energies is variable over time and depends on the kind of material, its properties and volume. As a result, the accuracy and reliability of the measurement results are significantly reduced.

The disadvantage is that the sensitive element is located across the flow of the measured material. As a result, this device (with such a design and arrangement of elements) can only be used for in-line measurement of the moisture content of materials and is unsuitable for measuring the moisture content of individual soil samples in the field.

Another disadvantage is the lack of a global positioning module in the device, which makes it impossible to determine the coordinates of moisture measurement points and map soil moisture in the field.

The objective of the invention: improving the reliability of measurements while ensuring mass measurements of moisture, the versatility of the device to measure the moisture of various types of soils, and also the ability to determine the coordinates of the points of sampling for measuring soil moisture.

The objective of the invention is solved by the following set of features of the proposed device. The proposed device, like the prototype, contains a housing, a power unit for a microwave emitter, a microwave emitter connected to the working chamber. On the opposite side of the working chamber relative to the microwave emitter, there is a sensing element (microwave radiation detector) that measures the level of microwave radiation passing through the test sample, a data processing unit by which its moisture is determined.

In contrast to the known, in the proposed device, the microwave emitter, the sensitive element (microwave radiation detector) and the working chamber are interconnected and together form a sealed resonant waveguide. The working chamber, which is built into the waveguide, has an access window through which a dielectric capacitance with a sample of soil is installed, the moisture content of which must be measured. In this case, the microwave emitter is separated from the working chamber by means of a dielectric membrane, which protects it from mechanical damage by particles of the test material. The proposed device also contains a global positioning module for determining the coordinates of the points of measurement of soil moisture.

This set of features of the proposed device solves the problem posed by the invention:

- increases the reliability and accuracy of measuring soil moisture while ensuring mass measurements. Since the microwave emitter and the sensitive element (microwave radiation detector) are interconnected and form a sealed (for electromagnetic waves) waveguide containing a resonator and a working chamber separated by a dielectric membrane. Since the waveguide is a resonator, i.e. scattering and absorption of electromagnetic energy in its walls and in the surrounding space are minimal. Increasing the reliability of measurements is carried out by maintaining a stable frequency of microwave radiation at 2.45 GHz (the frequency at which electromagnetic energy is absorbed by water molecules). Moreover, the measurement time is from 1 to 5 seconds, which allows for a high speed of measurements and, accordingly, their mass;

- increases the versatility of the device, because Microwave radiation with a frequency of 2.45 GHz is most effectively absorbed only by water, and not by mechanical particles of the soil, and the intensity of absorption does not depend on the type and concentration of salts contained in the soil, i.e. from the concentration of soil electrolytes;

- provides the ability to coordinate points of measurement of soil moisture, because the proposed device contains a global positioning module that allows you to fix and save to a removable drive the coordinates of the points of measurement and the route of movement of the device.

In FIG. 1 shows a diagram of the proposed microwave device for measuring soil moisture, FIG. 2 - flow chart of the proposed device.

The proposed device includes a housing 1, in which the power unit of the microwave emitter 2 is located (with a step-up transformer, voltage multiplier, high-voltage fuse, etc.), a microwave emitter 3 with a resonator waveguide of the resonator chamber 4 connected to the working chamber 7 through a dielectric membrane 5 On the opposite, relative to the microwave emitter 3, the side of the working chamber 7 is a microwave radiation detector 8, which measures the level of microwave radiation and through the data processing unit 9 displays the data on the display panel 1 0. A container 6 is made in the working chamber 7, made of a dielectric material, into which a soil sample is poured, the moisture content of which must be measured. The dielectric capacitance 6 is installed in the working chamber 7 through the access window 11. The microwave emitter 3 is controlled using the control panel 12. The global positioning module 13 determines the coordinates of the humidity measurement point and transmits a signal to the data processing unit 9.

Thus, in fact, the device is a waveguide, on one side of which a microwave emitter of electromagnetic waves is installed, and on the other a detector, and a soil sample is installed in the waveguide (Fig. 2).

The device operates as follows (Fig. 2).

A soil sample, the moisture content of which must be measured, is placed in a dielectric container 6 and installed in the working chamber 7 through the access window 11. The mass of the controlled soil sample is preliminarily calculated. Next, using the control panel 12, the microwave emitter 3 is launched for a time of about 3 s, which is necessary to measure the radiation intensity using the microwave radiation detector 8. The signal from the microwave radiation detector 8 enters the data processing unit 9, where it is also converted in a digital code, transmitted to the soil moisture indicator 10 and / or recorded on a removable storage medium. Thus, on the moisture indication panel 10, the analyzed and processed signal is displayed as a parameter of soil moisture. Then the microwave emitter 3 is turned off, and a controlled soil sample is removed from the working chamber 7.

Information sources

1. Microwave moisture meter LMA-200PM. [Electronic resource]: http://somet.ru/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=42&category_id=8&option=com_virtuemart&Itemid=68&lang=en (accessed: 12.16.2016).

2. Microwave moisture meter brand MW 1000. [Electronic resource]: http://www.europribor.com/component/page,shop.product_details/flypage,shop.flypage/product_id,130/category_id,28/option,com_virtuemart/ Itemid, 37 / (circulation date: 12.16.2016).

3. Patent for the invention of the Russian Federation No. 2154816, G01N 22/04. Method and device for continuous measurement of moisture content of bulk product / X. Tolber, R. Lehmann, R. Muller. - Date of publication 08/20/2000

Claims (3)

1. Microwave device for measuring soil moisture, comprising a housing in which the power unit of the microwave emitter is located, a microwave emitter connected to the working chamber, a microwave radiation detector located in the working chamber opposite to the microwave emitter, a data processing unit the fact that the microwave emitter contains a resonator chamber and is connected through a dielectric membrane to the working chamber, thereby forming a sealed resonant waveguide connecting it to the microwave radiation detector, while the working chamber is completely located in the waveguide, and through the access window into the working chamber, a test soil sample is installed, enclosed in a dielectric capacitance. 2. The microwave device according to claim 1, characterized in that the microwave radiation detector is connected to the display panel via a data processing unit. 3. The microwave device according to claim 1, characterized in that the device is further provided with a global positioning module associated with the data processing unit.

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