SU899753A1 - Sensor for determining hydro-physical properties of soils - Google Patents

Description

(54) SENSOR FOR DETERMINATION OF HYDROPHYSICAL CHARACTERISTICS OF SOILS

one

This invention relates to technical physics and can be used in agriculture and construction.

A sensor is known for determining the hydrophysical characteristics of soils, including a gypsum screen with a filler with electrodes placed in it, which are connected by electrical wires to a measuring device.

Ion exchange resins, for example, KU-2, AN-2F, saturated with ions 1, are used as a filler.

The disadvantage of this sensor is the limited range of research and the short-term nature of their use.

The closest in technical essence and the achieved result to the proposed is a sensor for determining the hydrophysical characteristics of soils, including a porous tip connected to it by means of a strain gage tube filled with liquid, a measuring system and a control unit 2.

The disadvantage of this sensor is the low accuracy of the study and the limited range of application for ground conditions.

The purpose of the invention is to increase the accuracy and range of the study.

This goal is achieved by the fact that in a known sensor for determining the hydrophysical characteristics of soils, including a porous tip connected to it by means of a strain gauge tube filled with liquid, a measuring system and a control unit. The porous tip is made of a composite of internal and

10 external sections separated by a waterproof partition and a semipermeable membrane and provided with an additional strain gauge tube with liquid connected to the measuring system and paired electrodes placed in

15 external and internal sections located on one side of the tip and connected with the control unit, the measuring device being equipped with a lever system with shut-off flaps that interact with the end faces of strain gauges

Claims (2)

 tubes, each of which is installed respectively in the outer and inner sections located on the other side of the tip, while the pair electrodes of the outer tip section are equipped with pair electrodes. The drawing shows the proposed sensor. The sensor includes a porous tip 1, divided into internal sections 2 and 3. and external sections 4 and 5 by a waterproof partition 6 and a semi-impermeable membrane 7, for example, from a sediment film. Sections 2, 4 and 4 have paired electrodes 8, 9, and 10 connected by wires AND to the control unit 12, and sections 3 and 5 have strain gauge pipes 13 and 14 connected to the measuring system 15, equipped with a membrane 16, a slider 7 , a rheostat 18, locking covers 19 and 20, connected by a two-arm lever 21 on support 22. Measuring system 14 is connected by wires 23 to a control unit. The sensor works as follows. The sensor is immersed in the ground. From the electrodes 8, 9 and 10, the readings of the electrical conductivity, respectively, of the inner section 2, the outer section 3 of the porous tip and the soil are taken. Moreover, due to the presence of a semi-impermeable membrane 8 with osmotic lattice properties, the salt concentration in the inner part of porous tip 1 is zero, and in its outer part due to ion diffusion, it is equal to the concentration of dissolved salts in the soil. The concentration of dissolved salts of the soil is determined from the difference in the electrical conductivity readings from electrodes 8 and 10. In addition, the magnitude of the difference in readings from these electrodes is a correction from the effect of salts on the readings from electrodes 9 in the soil, which takes into account its moisture. Thus, the measuring equipment of the control unit 12 connected to the electrodes 8, 9 and 10, corresponding to this, is recorded in a known manner, characterizing the soil moisture, taking into account the concentration of dissolved salts. The difference in the readings of electrical conductivity obtained from electrodes 8 and 9 is due to the different porosity of the soil and the probe under study, as well as their different physicochemical nature. But since the influence of the physico-chemical nature of the material is constant and easily taken into account, and the porosity of tip 1 is a predetermined value, the difference in readings from electrodes 8 and 9 on the corresponding scale of the measuring equipment of control unit 12 determines the data on the porosity of the soil being studied at this point . Due to the fact that the temperature in all places of the sensor, where the electrical conductivity is measured, is the same, on the difference in readings obtained from the electrodes, the effect of temperature is neglected. In the first position, when the spring-loaded cover 20 under the action of the spring locks the strain tube 14, and the tube 13 is open, the vacuum from the latter acts on the membrane 16, causes the slider 17 connected with it to move along the rheostat 18, the signal from which the wires 23 flow to the measuring apparatus block 9 control. At the same time, indications are drawn about the suction force of the soil, together with the strength of the osmotic attraction of water, moisture, dissolved salts, behind the semipermeable membrane 7. When an electrical signal comes through the wires 23 from the control unit 12, the solenoid-type cover 19 attracts the strain gauge tube 13 and accordingly, through the double-arm lever 21, the tube 14 opens, which gives indications of the suction force of the soil. The difference in readings from strain gauge tubes 13 and 14 provides information on the effect of salinity on the ingress of moisture to plants. Partition 6 prevents the meter from being distorted from the electrodes due to the ingress of water from the strain tubes. Thus, the presence of a semipermeable membrane (os.motic lattice), three pairs of electrodes in different conditions, strain gage tubes with closures, provides a constant, more reliable about the soil moisture, their suction force, porosity and concentration of dissolved salts, due to the reliability of the osmotic lattice, such as the enclosures of the electrodes and the strain tube in the inner part of the porous body, from the effect of the concentration of dissolved salts and the comparison of readings taken from the electrodes and strain tubes. The sensor for determining the hydrophysical characteristics of the soil as compared to the known does not require the consumption of ions, is more durable, additionally gives indications of the suction pressure, the porosity of the soils and the concentration of dissolved salts, more accurate moisture data, regardless of the type of soil, which is of great importance when developing mathematical models of water regime prediction in soils, in particular, in growing conditions of plants using hydroponics. Claim 1. Sensor for determining the hydrophysical characteristics of soils, comprising a porous tip connected to it by means of a strain-gauge tube filled with liquid, a measuring system and a control unit, characterized in that, in order to increase the accuracy and range of studies, the porous tip is made of internal and external sections separated by a waterproof partition and a semipermeable membrane and provided with an additional strain gauge tube with liquid with a measuring system and paired electrodes located in the outer and inner sections located on one side of the handpiece and connected to the control unit, the measuring device is equipped with a lever system with shut-off covers that interact with the ends of the strain gauge tubes, each of which is installed respectively in external and internal sections located on the other side of the tip-. 2. The sensor according to claim 1, characterized in that the pair electrodes of the outer tip section are equipped with outer pair electrodes. Sources of information taken into account in the examination 1. USSR author's certificate number 195707, cl. G 01 N 27/40, 1967. 2. USSR author's certificate No. 553563, cl. G 01 N 1/11, 1977 (prototype).