RU2069344C1 - Device measuring density - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: invention is meant for measurement of density of various suspensions by hydrostatic method with the use of piezoelectric instrument. Leak-proof chamber is manufactured in the form of bell mouth of conical shape, transducer placed on measuring part of piezotube and made in the form of hollow cylinder including set of low-current induction coils arranged in sequence. Float is fitted with short-circuited turn and register is manufactured in the form of interrogation-counting electron circuit. Parameters of device are chosen from conditions $$$; L=0.01H; $$$, where $$$ is area of elastic membrane; $$$ is area of section of piezotube; H is base (depth of lowering) of piezotube; L is spacing between induction coils; $$$ is height of induction coil; $$$ is height of short-circuited turn. For provision of test of registering electron circuit directly in process of operation of device transducer may be fabricated separable, measuring part of piezotube may have scale of divisions corresponding to value of spacing between induction coils. Device may also be equipped with second piezotube. In this case corresponding induction coils of transducers of both piezotubes should be electrically connected into half-bridge. EFFECT: expanded application field. 3 cl, 5 dwg

Description

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

 Known devices for measuring the density of suspensions [1], which are based on the principle of balancing the weight of a suspension column of a certain height and air pressure, issued into a piezotube from a collector.

 These devices contain a collector, piezotubes, pneumatic resistances. 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 reduces or increases the air flow by changing the resistance until the pressure difference in the differential pressure chambers is zero.

 The disadvantage of such devices is the relative complexity of the density measurement process, which is caused, on the one hand, by the complexity and duration of the process of balancing the air pressure in the piezotubes, and on the other, by the need for additional devices to avoid various errors (changing the base, the presence of different resistances in different parts of the tank, etc. d.).

The closest technical solution, selected as a prototype, is the device described in [2]
This device densitometer contains a ferromagnetic float placed in a hollow shaft (piezotube), which is filled with liquid. The movement of the float is determined using a differential transformer sensor. The end of the shaft (piezotube) immersed in the test suspension is connected to sealed chambers, which are separated from the test fluid by elastic membranes.

 The density of the test suspension is measured using a tachometer (recorder).

 The described device has a significant drawback relative complexity of density measurement, due to the need to ensure rotation of the hollow shaft with hermetic chambers and membranes.

 An object of the present invention is to simplify a density measurement process.

; L=0,01 H, l_к=l_в=0,5•L,
где S_м площадь эластичной мембраны;
S_п площадь сечения пьезотрубки;
H база (глубина погружения) пьезотрубки;
L шаг между катушками индуктивности;
l_к высота катушки индуктивности;
l_в высота короткозамкнутого витка.The problem is achieved in that in a density measuring device containing a piezotube, the end of which, immersed in the test suspension, is connected to a sealed chamber separated from the test suspension by an elastic membrane, a float placed on the neutral line of the sensor, and the recorder sealed chamber is made in the form a bell-shaped cone, the sensor is located on the measured part of the piezotube and is made in the form of a hollow cylinder with a set of sequentially located low-current inductance coils, a float equipped with a short-circuited coil, and the registrar is made in the form of a questioning-recalculation electronic circuit, while the device parameters are selected based on the conditions:

; L = 0,01 H, l = l _{to a} = 0,5 • L,
where S _{m the} area of the elastic membrane;
S _p the cross-sectional area of the piezotube;
H base (immersion depth) of the piezotube;
L pitch between inductors;
l _{to the} height of the inductor;
l _{to the} height of the closed loop.

 To ensure verification of the recording electronic circuitry directly during the operation of the device, the sensor can be made removable, and on the measured part of the piezotube a scale of divisions corresponding to the step value between the inductance coils is applied.

 The device for measuring density can be equipped with a second similar piezotube placed along the immersion depth at some distance from the first, while the corresponding inductance coils of the sensors of both piezotubes must be electrically connected in a half-bridge.

 The attainability of the goal is due to the fact that the claimed features together, their location and geometric dimensions allow you to determine the density of the suspension under investigation as simply as possible, namely, by the number of steps between the inductors displayed on the digital display of the recorder. Drawing a scale with divisions corresponding to the step between the inductance coils on the measuring part of the piezotube allows, when removing the sensor, to simultaneously visually determine the density and monitor the entire measuring part during operation of the device.

 Comparison of the claimed device with the prototype shows that the claimed device is distinguished by the structural design of the sealed chamber, float, sensor, recorder, their placement and geometric dimensions of the device.

 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 this technical field did not reveal the signs that distinguish the claimed solution with the prototype, which allows us to conclude that the criterion of "inventive step" is met.

 The inventive device is industrially applicable, because it can be used in industry, agriculture, healthcare and other sectors of the economy where it is necessary to measure the density of the suspension under investigation.

 The invention will be more apparent from the drawings. In FIG. 1 presents the inventive device in General. In FIG. Figure 2 shows a piezotube with a printed scale of divisions assembled with a bell and an elastic membrane. In FIG. 3 graph of the deflection of the membrane. In FIG. 4 schematically illustrates the use of 2 piezotubes. In FIG. 5 diagram of the electrical connection of the inductors of 2 piezotubes.

 The claimed device (Fig. 1) contains a piezotube 1, the lower end of which is connected to a socket 2, separated from the test suspension 3 by an elastic membrane 4. The sensor 5 is made in the form of a hollow cylinder with a set of consecutive low-current inductance coils 6. The float 7 is equipped with a short-circuited coil 8 The recorder 9 is made in the form of a questioning-counting electronic circuit that calculates the number of steps from a coil corresponding to a zero level (for example, I) to a coil (for example, II), near which there is a short closed loop 8 of the float 7.

 The sensor 5 can be made removable, then on the measured part of the piezotube 1 (Fig. 2) plotted 12, corresponding to the value of step L, between the inductors 6.

 In the case when it is not possible to organize a suspension column of the required height H or the discharge level does not remain stable, two piezotubes (Fig. 4) 1 and 13 should be used. The piezotube 13 is placed at a distance H from the depth of immersion relative to the first.

 In this case, the corresponding inductance coils 6 of the sensors 5 are electrically connected in a half-bridge (Fig. 5), and the interrogation device 9 calculates the number of steps from the coil, near which there is a short-circuited turn of one piezotube to a short-circuited turn of another.

 The number of steps between the inductance coils determines the density of the test suspension.

 The geometric dimensions of the claimed device are selected experimentally, based on the conditions for ensuring a minimum error.

 So the optimal step size between the inductance coils L and the corresponding divisions of the scale applied to the measured part of the piezotube is the hundredth part of the immersion depth H of the tube 1 in suspension 3, i.e. L = 0.01 H.

(2)
или (в процентах)

Уравнение (1) справедливо в случае, когда можно пренебречь силой упругого сопротивления мембраны 4, точнее ее влиянием на гидростатическое равновесие соответствующих столбов суспензии и контрольной жидкости.At the same time, the column of control liquid in the piezotube rises to a height (H + ΔH). In accordance with the laws of hydrostatics:
Q _c • H = Q _in • (H + ΔH), (1)
where Q _{c is the} density of the suspension;
Q _{in the} density of the control fluid in the tube (e.g. water)
Hence the density of the suspension:

(2)
or (percent)

Equation (1) is valid in the case when the strength of the elastic resistance of the membrane 4 can be neglected, more precisely, its effect on the hydrostatic equilibrium of the corresponding suspension columns and control liquid.

 It is to fulfill this level that the sealed chamber connected to the lower end of the piezotube is made in the form of a bell 2 of a conical shape.

. Задавая еще большее соотношение

(15 30) можно получить пьезотрубку, мембрана которой практически не будет прогибаться в процессе измерения, а следовательно, и погрешность измерений будет минимальной.The rigidity of the membrane is clearly nonlinear. In FIG. Figure 3 shows in general terms the dependence of the resistance force F (rigidity) of a membrane on its displacement ξ relative to its neutral (horizontal) position. It can be seen from the presented dependence that if a small displacement of the membrane near the neutral position (x is negligible) is ensured, then the resistance F of the membrane will also be vanishingly small, and therefore the influence of the latter on the measurement process can be neglected. For example, if the diameters of the tube d and the bell D differ by more than 15 times (D> 15d), then the membrane and tube areas differ by more than 200 times (S _m > 200 S _p ). Therefore, when registering the density of the suspension, for example, Q = 1200 kg / m ³ at H = 0.5 m, the claimed device allows to obtain an excess of the column of the control liquid (for example, water) DH == 100 mm, while the deflection of the membrane will be

. Setting an even greater ratio

(15 30) it is possible to obtain a piezotube, the membrane of which will practically not bend during the measurement process, and therefore the measurement error will be minimal.

 The selected step size allows you to measure the density with an accuracy of fractions of a percent. The piezotube has an inside hole of d≈2-3 mm to pass the control fluid. The hole at the same time is also hydraulic resistance, damping the oscillations of the column of the control fluid from disturbance (through the membrane) from the side of the suspension during measurements in a moving stream. The measured part of the piezotube has an internal diameter equal to 10 mm, which is necessary to accommodate the float.

 The inventive device operates as follows.

 As the float moves (with a change in the density of the suspension, the level of the control liquid in the measured part of the piezotube also changes), the corresponding inductors are shielded by a short-circuited coil of the float, their inductance changes dramatically (drops by about 30%), which is easily detected by the interrogation circuit.

 The authors created a prototype of the inventive device for determining the density of milk of lime.

The depth of immersion of the piezotube is 500 mm, the pitch between the inductors was 5 mm, while the size of the coils along the winding cross-section is 6 mm ² (2.5 x 2.5 mm). The interrogation circuit is designed so that the interrogation of changes in the inductance of all coils is a fairly short time ≈5. 15 sec

The number of steps is numerically equal (in percent) to the density of the suspension under study, while the readability was 0.5%
Summing up all of the above, we can conclude that the use of the inventive device allows you to simply measure the density of any test suspension.

Claims (3)

1. A device for measuring density, containing a piezotube, the end of which, immersed in the test suspension, is connected to a sealed chamber separated from the test suspension by an elastic membrane, a float located on the neutral line of the sensor, and a recorder, characterized in that the sealed chamber is made in the form a bell-shaped cone, the sensor is located on the measured part of the piezotube and is made in the form of a hollow cylinder with a set of sequentially located low-current inductance coils, the float is equipped with a short-circuit Knuth coil and configured as a registrar interrogatory-scaler circuitry, wherein the device parameters are selected based on the conditions:
S _m / S _p ≥200; L = 0.01H; l _to = l _in = 0,5L,
where S _{m the} area of the elastic membrane;
S _p the cross-sectional area of the piezotube;
H base (immersion depth) of the piezotube;
L pitch between inductors;
l _{to the} height of the inductor;
l _{to the} height of the closed loop.  2. The device according to claim 1, characterized in that the sensor is removable, and a graduation scale is applied to the measuring part of the piezotube corresponding to the step value between the inductance coils.  3. The device according to claims 1 and 2, characterized in that it is equipped with a second similar first, piezotube placed along the immersion depth at a distance from the first, while the corresponding inductance coils of the sensors of both piezotubes are electrically connected in a half-bridge.

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