RU2137109C1 - Device measuring density - Google Patents

Abstract

FIELD: measurement technology, measurement of density of various suspensions and solutions by hydrostatic method with the use of piezometric instrument. SUBSTANCE: device measuring density has two leak-proof chambers positioned at different levels in tested medium. One wall of each chamber is made in the form of elastic membrane. Each piezotube is joined with lower end to proper chamber. Each piezotube carries level gauges determining level of tested liquid. Upper parts of both piezotubes are sealed. Each piezotube is divided at point of installation of level gauges into two parallel parts arranged in symmetry to vertical axis in mutually perpendicular planes crossing along symmetry axis. Each parallel part of each piezotube has level gauge. Leak-proof chamber are mounted one below another on one vertical axis. Chambers and lower parts of piezotubes are filled with heavier test liquid and upper parts of piezotubes above middle of level gauges are filled with lighter liquid that is immiscible with first liquid. Dielectric permittivity of first and second liquids differs by more than one order. Information processing unit subtracts signals corresponding to levels of separation of test liquids in first and second piezotube, sums up these signals and divides obtained difference by sum of these signals. EFFECT: enhanced precision of density measurement thanks to increased noise immunity and widened measurement range. 1 cl, 4 dwg

Description

 The invention relates to measuring equipment and is intended to measure the density of various suspensions and solutions by the hydrostatic method using a piezometric device.

 Known devices for measuring the density of suspensions and solutions [1], which are based on the principle of balancing the weight of a suspension column of a certain height and air pressure supplied to the piezoelectric tubes from the collector. These devices contain a collector, piezotubes, pneumatic resistance. When the density of the suspension changes, the resistance of the piezotubes changes, causing a decrease or increase in the flow rate of air flowing through the piezotubes. The pressure difference is measured by a differential pressure gauge, and the automatic tracking system by changing the resistance decreases or increases the air flow until the pressure difference in the differential pressure chambers is zero.

 The disadvantage of such devices is the relatively narrow range of measurements due to insufficient noise immunity to external factors, for example, external pressure.

 The closest technical solution, selected as a prototype, is a "Device for measuring density" [2].

 This device contains two sealed chambers located at different levels in a controlled environment, one wall of which is made in the form of an elastic membrane, two piezotubes, each connected with its lower end to its chamber, sensors installed on each piezotube to determine the level of the control fluid in the piezotubes, block information processing and registrar.

 The aim of the present invention is to improve accuracy by increasing noise immunity, sensitivity and expanding the measurement range.

 This goal is achieved by the fact that in a device for measuring density, containing two sealed chambers located at different levels in a controlled environment, one wall of which is made in the form of an elastic membrane, two piezotubes, each connected with its lower end to its own camera, each mounted on its own piezotube sensors for determining the level of control fluid in piezotubes, an information processing unit and a recorder, piezotubes in the upper part are hermetically closed to each other, sealed chambers and the lower part the piezotubes to the middle of the level sensors are filled with one heavier control fluid, and the upper part of the piezotubes is filled with another lighter, immiscible with the first fluid, the dielectric constants of the first and second fluids are more than an order of magnitude different, sealed chambers are mounted on the same vertical axis one below the other, each of the piezotubes in the field of installation of the level sensors is divided into two parallel symmetrical with respect to the vertical axis, in mutually perpendi planar planes, parts, level sensors intersecting along the vertical axis of symmetry are capacitive, each with two working electrodes located along each part of the piezotube and three guard electrodes, two of which are parallel to the working electrodes, and the third ring electrode is lower than the working electrodes in the common part of its piezotube, capacitive sensors belonging to one piezotube are connected in parallel to each other, all guard electrodes are galvanically connected to the common point of the processing unit information boxes in which the signal corresponding to the separation level of control liquids in one piezotube is subtracted from the signal corresponding to the separation level of control liquids in another piezotube, the summation of signals corresponding to the separation levels of control liquids in both piezotubes is divided by the result of subtraction by the summation result.

 The achievement of this goal is due to the fact that the inventive device allows due to the hermetic closure of the piezotubes in their upper part to each other, to increase the noise immunity to pressure changes of the controlled medium and to expand the measurement range with equal sensitivity by more than two times, filling the sealed chambers and piezotubes from bottom to middle level sensors with a heavier control liquid, and the upper part of the piezotubes with a lighter, immiscible with the first, liquid, can increase the sensitivity spine; the difference in permittivities by more than an order of magnitude allows one to obtain increased sensitivity of a capacitive level sensor, the installation of sealed chambers on one vertical axis one above the other, and the separation of each piezotube into two parallel symmetrical vertices of symmetry, parts, as well as the connection of capacitive sensors belonging to one piezotube , parallel to each other, eliminate the error from the non-vertical installation of the device in a controlled environment, the presence of three security electrodes galvanically connected to a common information processing point, can increase the noise immunity from unauthorized electrical connection of the capacitive transducer to the ground through the lower control fluid and the test fluid; the presence in the information processing unit of the operation of dividing the difference of signals corresponding to the separation level of control liquids in piezotubes by the sum of these signals allows reducing errors by more than an order of magnitude from the effect of temperature on the density and permittivity of control liquids.

 Comparison of the claimed device with the prototype shows that the claimed device is characterized in that the piezotubes in its upper part are closed to each other, the sealed chambers and piezotubes in the lower part to the middle are filled with a heavier control fluid, and the upper part of the piezotubes is filled with a lighter, immiscible with the first , liquid, while the dielectric constant of the first and second liquids are more than an order of magnitude different from each other, sealed chambers are installed on the same vertical axis under each other ohm, each piezotube in the installation area of the level sensor is divided into two parallel symmetrical to the vertical axis in mutually perpendicular planes intersecting along the vertical axis of symmetry, parts, level sensors are capacitive, each with two working electrodes located along the piezotube and three guard electrodes two of which are parallel to the working ones, and the third ring is located below the working electrodes in the common part of the piezotube, capacitive sensors, belong hedgehogs to one piezotube are connected in parallel, all guard electrodes are galvanically connected to a common point of the information processing unit, the information processing unit performs the operation of dividing the difference of the signals corresponding to the section level of the control liquids in the piezoelectric tubes by the sum of these signals.

 Thus, the claimed device meets the criteria of the invention of "novelty." Comparison of the claimed device not only with the prototype, but also with other technical solutions in the art did not reveal the signs that distinguish the claimed device from the prototype, which allows us to conclude that the criterion is "inventive step".

 The inventive device is industrially applicable, as it can be used in various fields of industry - agriculture, healthcare, biology, ecology and other areas where it is necessary to measure the density of suspensions and solutions.

 The invention will be more clear from the above figures.

 In FIG. 1 presents the inventive device in General.

 In FIG. 2 is a diagram of a hydrostatic converter.

 In FIG. 3 is a structural diagram of a level sensor.

 In FIG. 4 is a diagram for connecting a sensor to an information processing unit.

The inventive device for measuring density contains tight chambers 1 and 2 with elastic membranes 3 and 4, separating chambers 1 and 2 from the test suspension 5, piezotubes 6 and 7, each connected with its lower end to its chamber 1 and 2, two sensors 8 and 9, installed on two parallel symmetrical vertical axis parts 10, 11 of the piezotube 6 to determine the level of separation of the control fluids in the piezotube 6, two sensors 12, 13 mounted on two parallel vertical axis parts of the piezotube 7 to determine the level of the control section liquids in the piezotube 7, the information processing unit 16, the recorder 17. The piezotubes 6 and 7 in the upper part are closed to each other, the sealed chambers 1 and 2 and the lower part of the piezotubes 6 and 7 to the middle of the level sensors 8, 9, 12, 13 are filled with one a heavier control fluid 18, and the upper part of the piezotubes 6 and 7 is filled from the middle of the level sensors 8, 9, 12, 13 to the upper cut of another lighter, immiscible with the first, fluid 19; the dielectric constant ε _{1 of the} first liquid 18 is more than an order of magnitude different from the dielectric constant ε _{2 of the} second control liquid 19; level sensors 8, 9, 12, 13 are made capacitive, each with two working electrodes 20 and 21, 22 and 23, 24 and 25, 26 and 27 located on the parallel upper parts 10, 11, 14, 15 of the piezo tubes 6 and 7 along their length and three guard electrodes 28, 29, 30; 31, 32, 33; 34, 35, 36; 37, 38, 39; the first two electrodes 28, 29; 31, 32; 34, 35; 37, 38; located parallel to the working electrodes 20, 21; 22, 23; 24, 25; 26, 27, and the third ring electrodes 30, 33, 36, 39 are located in the lower part of their piezotube 6 and 7 at the lower cut of the parallel parts 10, 11 and 14, 15, the electrodes 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 are galvanically connected to a common point of the information processing unit.

To explain the principle of operation and operation of the inventive device, it is necessary to solve the corresponding hydrostatic equations with respect to the system: the test liquid, pressurized chambers 1 and 2, piezotubes 6 and 7 with the corresponding columns of control immiscible liquids 18 and 19 (see Fig. 2). Denote:
h - measurement base, m;
Δh is the immersion depth of the sealed chamber 2;
h ₁ is the distance from the midline of the sealed chamber 2 to the dividing line of immiscible liquids 18 and 19 in the piezotube 6, m;
h ' ₁ is the distance from the dividing line of immiscible liquids 18 and 19 in the piezotube 6 to the upper end of the piezotube 6, m;
h ₂ is the distance from the midline of the sealed chamber 2 to the dividing line of immiscible liquids 18 and 19 in the piezotube 7, m;
h ' ₂ is the distance from the separation line of immiscible liquids 18 and 19 in the piezotube 7 to the upper end of the piezotube 7, m;
P _in - external pressure, Pa.

Учитывая, что (h₁ - h₂) = x, a (h'₁ - h'₂) = -x, из (1) получим
ρ•h = X(ρ₁-ρ₂)+ρ₁•h; (2)

Если в качестве искомого принять ρ_x , то получим из (2)

Полученные зависимости (2), (3) и (4) позволяют выявить преимущества заявленного устройства. Из (3) следует, что X может принимать как положительные значения при ρ_x > ρ₁, так и отрицательные при ρ_x < ρ₁, при ρ_x = ρ₁ X = 0 - уровни жидкостей в пьезотрубках совпадают с "O" (см. фиг. 2) , а пределы измерения изменяются от

до

Диапазон измерения плотностей составляет:

что, как минимум в два раза, превышает диапазон измерения у прототипа при условии равной с ним чувствительности. Кроме того, из (3) следует, что показания X устройства измерения плотности не зависят ни от внешнего давления P_в, ни от глубины погружения Δh герметичных камер 1, 2 в исследуемую суспензию 5.The equation of hydrostatic equilibrium of the corresponding columns of immiscible media with respect to the pressure on the midline of the sealed chamber 2 is written as follows:

Given that (h ₁ - h ₂ ) = x, a (h ' ₁ - h' ₂ ) = -x, from (1) we get
ρ • h = X (ρ ₁ -ρ ₂ ) + ρ ₁ • h; (2)

If we take ρ _x as the desired one, then we obtain from (2)

The obtained dependencies (2), (3) and (4) allow us to identify the advantages of the claimed device. From (3) it follows that X can take both positive values for ρ _x > ρ ₁ and negative for ρ _x <ρ ₁ , for ρ _x = ρ ₁ X = 0 - the liquid levels in the piezotubes coincide with “O” ( see Fig. 2), and the measurement limits vary from

before

The density measurement range is:

which is at least two times greater than the measuring range of the prototype, subject to equal sensitivity with it. In addition, it follows from (3) that the readings X of the density measuring device depend neither on the external pressure P _c nor on the immersion depth Δh of the sealed chambers 1, 2 in the test suspension 5.

Из (6) видно, что К зависит только от базы h и разности плотностей контрольных жидкостей 18 и 19 и не зависит ни от внешнего давления, ни от глубины погружения камер 1, 2. Габариты заявляемого устройства при условии равных чувствительностей и равных диапазонов, по сравнению с прототипом, могут быть уменьшены. База h в

раз, а длина пьезотрубок уменьшена более чем в четыре раза. Пределы и диапазон измерения плотности исследуемой суспензии, а также чувствительность устройства можно менять подбором плотностей несмешивающихся контрольных жидкостей и базы измерений h. Чувствительность устройства также возрастает с увеличением разности диэлектрических проницаемостей ε₁ контрольной жидкости 18 и ε₂ жидкости 19.The sensitivity of the device will be:

From (6) it can be seen that K depends only on the base h and the difference in densities of the control liquids 18 and 19 and does not depend either on external pressure or on the immersion depth of chambers 1, 2. The dimensions of the claimed device, provided equal sensitivity and equal ranges, Compared with the prototype, can be reduced. Base h in

times, and the length of the piezotubes is reduced by more than four times. The limits and range of measuring the density of the suspension under study, as well as the sensitivity of the device, can be changed by selecting the densities of immiscible control liquids and the measurement base h. The sensitivity of the device also increases with increasing difference in permittivity ε _{1 of the} control fluid 18 and ε _{2 of the} fluid 19.

When the density of the investigated suspension 5 is greater than ρ ₁ , the liquid level 18 with a dielectric constant ε ₁ in the piezotube 6 increases, and in the piezotube 7 decreases. In this case, the capacitance between the electrodes 20 and 21, 26 and 27 of the piezotube 6 increases, and between the electrodes 24 and 25, 26 and 27 of the piezotube 7 decreases. The information processing unit generates a signal proportional to the difference between the mutual capacitance of the parallel-connected electrodes 24, 26 and 25, 27 and the mutual capacitance of the parallel-connected electrodes 20, 22 and 21, 23, as well as the sum of the same capacities, makes the difference of the capacitance by the sum of the capacities. The result of the transformations is proportional to the increment of the desired density Δρ _x , which makes it possible to obtain the density ρ _x = ρ ₁ + Δρ _{x of} the suspension under study 5. The guard electrodes 28, 29, 31, 32, 34, 35, 37, 38 reduce the edge effects of the containers, and the guard 30 , 33, 36, 39 make it possible to increase the noise immunity from unauthorized electrical connection of the capacitive converter to earth through the lower control liquid 18 and the test suspension 5.

 Thus, the claimed device allows to increase the measurement accuracy by increasing the sensitivity and noise immunity to the effects of external pressure, the non-vertical installation of the densitometer, temperature influence and electrical noise, to expand the measurement range, reduce the dimensions of the device.

Sources taken into account
1. V. N. Begunov, Yu.P. Zhukov and others. Automatic devices for measuring the concentration of suspensions. M .: Engineering, 1979, p. 28.

 2. RF patent N 20-69344 M.cl. 5 G 01 N 9/26 BI N 32, 1996 according to the application N 9401739/25 BI N 11, 1996

Claims (2)

 1. A device for measuring density, containing two sealed chambers located at different levels in a controlled environment, one wall of which is made in the form of an elastic membrane, two piezotubes, each connected with its lower end to its chamber, and sensors for determining the level of control liquids in the piezotubes installed each on its own piezotube, an information processing unit and a recorder, characterized in that the piezotubes in the upper part are hermetically closed to each other, each piezotube in the installation area is a sensor in the level it is divided into two parallel, located symmetrically with respect to the vertical axis in mutually perpendicular planes intersecting along the vertical axis of symmetry, parts, a level sensor is installed on each of the parallel parts of each piezotube, the sealed chambers are mounted on top of each other on the same vertical axis, the sealed chambers and the lower part of the piezotubes to the middle of the level sensors are filled with one heavier control fluid, and the upper part of the piezotubes above the middle of the level sensors are filled another lighter immiscible with the first liquid, while the dielectric constant of the first and second liquids are more than an order of magnitude different, the information processing unit additionally performs the operation of summing the signals corresponding to the separation levels of the control liquids in different piezotubes and dividing the difference of the signals corresponding to the separation levels liquids in different piezotubes, the sum of these signals.  2. The device according to claim 1, characterized in that the level sensors are capacitive, each with two working electrodes located along the piezo tube and three guard electrodes, two of which are parallel to the working electrodes, and the third ring electrode is located below the working electrodes in the common part of the piezotube, capacitive sensors belonging to one piezotube are connected in parallel, and all guard electrodes are galvanically connected to the common point of the information processing unit.

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