SU777555A1 - Liquid density measuring device - Google Patents

Description

The invention relates to measuring equipment, in particular to devices for measuring the density (concentration) of liquid media in irrigation and drainage, and can be used in those industries in which 5 control of the density of the liquid is a necessary condition for the process.

A device for measuring the density of liquid media is known, consisting of a piezometric tube immersed in a test medium at a certain depth and a differential pressure gauge [1].

The disadvantage of this device is the influence of the liquid level on the readings 15 of the device.

The closest in technical essence to the present invention is a device for measuring the density of liquid media, containing two piezometric 20 tubes, one of which is immersed in the test, and the other in the reference medium, air supply unit and differential pressure gauge [2].

However, in this device, the output signal of the densitometer is formed in the form of an analogue signal.

The aim of the invention is to improve the accuracy of measurement by obtaining a discrete output signal.

This goal is achieved by the fact that the device is equipped with a variable volume chamber with an unsealed piston located in it, four valves and a pneumatic throttle, while two valves with a pneumatic throttle between them are installed in the air supply line between the piezo tubes, the pneumatic throttle is connected to the chamber input, the output of which is connected between the third and the fourth valves, one of which is connected to the air supply unit, and the other to the atmosphere.

The drawing shows a schematic diagram of the proposed device.

Compressed gas from source 1 of compressed constant pressure gas sparges through piezometric tubes 2 and 3, immersed to a constant depth in vessels 4 and 5 with the studied and reference liquids, respectively. At the beginning of the measurement cycle, valves 6 and 7 are closed and valve 8 is opened. In this case, under pressure, the amount of compressed gas proportional to the immersion pressure of tube 2 is fed through open valve 9 and air throttle 10 into a variable-volume chamber AND containing an uncompressed piston 12. Under the action At this pressure, the piston moves at a constant speed. When the piston 12 reaches the level of installation of indicator 13 with a piston 12, the initial time of filling with compressed gas a certain volume of gas in the chamber 11 is fixed, moving further the piston reaches the installation location of indicator 14, after which the final time of filling of the chamber 11 is fixed.

The volume of filling the chamber 11 with compressed air when moving the piston 12 from the installation location of the indicators 13 and 14 is determined by the expression:

(1) about where Hi is the immersion level of tube 2; g — acceleration of gravity;

fig. - the density of the test fluid; t _x is the final filling time;

R - pneumatic resistance of the pneumatic throttle 10.

This ends the first measure step.

In the next step, valves 8 and 9 are closed and valves 6 and 7 are opened. Under the action of the compressed gas pressure from the source 1, the piston 12 displaces the previously filled volume of compressed gas through the pneumatic throttle 10, valve 7 and the tube 3 under the layer of the reference liquid. Using indicators 14 and 13 measure the start time of the emptying of the chamber 11. The emptied volume of gas is determined from the expression:

(3) (4) = ~ ^ H ₃ ? ₃ gdt, (2) where H ₂ is the immersion level of the tube 3; p _e - the density of the reference fluid.

Since the volumes of filling and emptying are equal to each other (1L = Y2), and the parameters R, Hi, H ₂ and g are constant values, integrating expressions (1) and (2), respectively, in the time interval from 0 to t _x and from 0 to t ₀ , we get:

RRoJx = or tx Re to P.r Βι

Thus, the output signal, which depends on the density of the medium being measured, is formed in the form of the ratio of the time interval of filling the chamber of variable volume depending on the density of the liquid under study to the time it is emptied through the layers of the reference liquid, i.e., by integrating piezometric pressures twice in time.

Since the integration of pressure in the piezometric tube 3 is a reference, expression (4) for a particular densitometer takes the form

NPO “Search” Order 2270/17 Ed. No. 530 Circulation 1033

H ₂ , * i't

Hi

By changing accordingly a pair of ₅ meters _re , Well, H ₂ and t ₀ , it is possible to change the sensitivity of the density meter in a wide range.

Claims (1)

Claim A device for measuring the density of a liquid, containing two piezometric tubes immersed in the test and reference medium, an air supply unit, 15 differential pressure gauge, characterized in that, in order to improve the measurement accuracy by obtaining a discrete output signal, the device is equipped with a variable-volume camera with it is not sealed by a piston, four valves and a pneumatic throttle, while two valves with a pneumatic throttle between them are installed in the air supply line between the piezo tubes, the pneumatic throttle is connected to the input of the chamber, the output of which is connected between the third and fourth valves, one of which is connected to the air supply unit, and the other to the atmosphere.