SU1608545A1 - Apparatus for measuring volumetric effects - Google Patents

Abstract

The invention relates to a measurement technique and allows the device to expand its functionality in zero gravity. The device provides the transformation of volume effects into the longitudinal deformation of the elastic element, which is carried out in the mode of relaxation of external stresses, and the measurement of the magnitude of this deformation using strain gauges. The device contains working and reference cells with bellows inserts installed in them, a loading mechanism consisting of a moving power screw and two elastic elements differentially associated with the cells, and a recording system including a dynamometer and strain gauges. 1 hp f-ly, 1 ill.

Description

The invention relates to a technique of measuring and thermophysical characteristics and can be used to measure the opinions of the volume of cooled, heated, or at constant temperature liquids, gases, biological vials and solid phase substances. The aim of the invention is to reduce measurement errors and the possibility of unit measurements under weightless conditions. The drawing shows a diagram of the proposed device.

/ device contains, the supporting column of the lower part of which is located 2- and reference 3 are dilatometric cylindrical K (jpnyca, respectively, inside which spacer inserts 6 and 7 are plug-in / 19. Cases 4 and 5 are suspended in movable 10 and 11 so that they are mounted on

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The supporting column fixed tappets 12 and 13 abut against plugs 8 and 9 of the bellows inserts 6 and 7. To measure the temperature of the solutions or in the ampoules 14 and 15 of the solid-phase samples and the two cells 2 and 3, they are equipped with resistance thermometers 16 and 17. A programmable change or stabilization of the temperature of the samples is carried out using a temperature-controlled chamber 18. In the upper part of the device, a loading mechanism 19 is located, consisting of an electric drive, a gearbox and a vertically moving power screw 20. The load from the latter is transmitted to cells 2 and 3 using grippers 10 and 11 through a load chain consisting of the upper elastic element 21, the stem 22 and the lower elastic element 23. In this case, the reference cell 3 is connected by a bracket 24 directly to the lower elastic element 23, and the working cell 2

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included in the load circuit through the dynamometer 25. The load is applied to it through the contact of the sleeve 26 with the supporting DISK.27, which can be moved along the rod 22 and installed on it before the experiment in one of the required positions. In order to maintain the working cell 2 in a fully unloaded state, a fixture 28 is moved along the support column in the device.

The volumetric effects are measured using both a dynamometer 25, and a small displacement sensor 29, turned on so that its body is connected to one end of the dynamometer 25 and the core to the other. The signal from the dynamometer 25 and the sensor 29 is recorded by a two-coordinate plotter, to the second coordinate of which a signal is sent from the resistance thermometer 16. To prevent the displacement sensor 29 from moving out of the linear zone, which is typical for measuring with high sensitivity, an automatic zero reset is provided in the device. It is implemented using a differential micrometer screw 30 associated with the sensor body 29, rotated by a stepper motor 31.

The device works as follows.

Dilatometric cells 2 and 3 on a special vacuum stand are filled with the test and reference solutions, respectively. In the study of solid-phase materials or biological tissues, they are placed in the working cell 2 in elastic ampoules 14. At the same time, samples of quartz, the volume of which is equal to the volume of the material under investigation, are placed in the reference cell 3 in the same ampoules 15. Thereafter, cells 2 and 3 are filled with dilatometric fluid according to standard procedures. The filled cells 2 and 3 are suspended on the grippers 10 and 11 so that the pushers 12 and 13 abut against the plugs 8 and 9. The elastic elements 21 and 23 are not tensioned, and the sleeve 26 connected to the working cell is in contact with the latch 28. In This moment is the installation of the support disk 27. Its position is determined by the experimental conditions, in particular, the load that must be applied to the working cell 2 in this experiment. Then the temperature-controlled chamber 18 is mounted, the initial temperature of the sample and the reference is necessary, and the cell loading process begins. This process consists of two stages. Continuous stretching occurs on the first ethane.

elastic elements 21 and 23 connected with the power screw, and the load is perceived only by the reference cell 3. This happens until the supporting disk 27 rising during the loading process does not touch the sleeve 26 connected to the clamp 28 connected through the bracket with the working cell 2. From this moment the loading of the working cell begins, and

the FR force acting on its circuit can be defined as

FR KiXi-K2X2 ..., (i)

where KI and K2 are the stiffness coefficients of the upper and lower elastic elements, respectively;

Xi and X2 - tension (elastic deformation) of elastic elements.

After reaching a predetermined load level FR FRI, which is fixed by a dynamometer 25, the loading mechanism 19 stops, the device is stabilized for several minutes and the measurement process begins.

The design of the device allows measurements of two types; in isothermal conditions and when scanning temperature at a given speed. The implementation of the second type of measurements in instruments operating in the relaxation mode is extremely

is difficult. This is due to the fact that the change in temperature of parts of the device, including the temperature, is dilatometric. liquid, leads to a change in the initial length of the load chain from

elastic elements and, as a result, changes in the load in this chain. As a result, errors arise due to the compressibility effects of the studied solutions. For example, when the temperature changes

cells with a volume of Vo 10 cm at АТ 100 ° С displacement of its body relative to a fixed pusher (fig. 1)

Ahi; 8VoAT / S -0,2cM, (2)

where / 3 is the coefficient of thermal volumetric expansion of the test solution, which in the case of aqueous solutions of biomolecules

 S is the effective cross section area of the bellows insert (, 5 cm). In the case of the use of conventional loading schemes using a single elastic element, even having very low values

stiffness coefficient KTV kg / cm, the change in load in the measuring circuit due to the displacement Ahi is

AFpi KI Ahi, 2kg.

(3)

This leads to a change in the volume of the study of the mobile solution due to the effect of compressing the mass by the value of AVv

 APRi. „-5, S S W where t is the compressibility factor, which is equal in this case

1c (4), it follows that the resolution of dilatometers using the traditional relaxation scheme is limited to 10%. Used in the proposed device, the loading circuit allows for this value. Based on (1) APRi value, we have

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Where

FRI Ki AXi-K2 AX2 (5)

 Ahi and АХ2 - changes nat - i of elastic elements 21 and 23 due to

The volume of the test and standard solutions, when their temperature changes, in the case of a change in the tension of the elastic element 23 consists of

AHg-Ahi + Ah2, (6)

hi and Ah2 are the changes in the tension of the element 23 due to the change in the volumes of the reference and reference solutions in someone's 1 3, respectively.

Substituting (6) and (5) to perform a-A FRI O, we obtain the ratio

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VIA l Pusa; Nepal (Ki + K2) Schoenge Bochei This is the working effect of them

K2

(7)

(7) it follows that in order to carry out the UFRI O, the vertical displacement of the reference cell 3 relative to the squeeze pusher 13 must be in / K2 greater than the corresponding shift in the process of measuring the housing 4 of the races 2 relative to the pusher 12. You can achieve by selecting the volumes and ( Urab) and reference (WET) cells or cross-sectional cross-section of bellows inserts so that they satisfy the condition

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with that heat and

VST Spa6 K2 + Kl Vpa6

The logical result can be obtained: the same ratio of the coefficients of the th volumetric expansion of the working ethanol (this

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conditions

K2 -f Kl K2

(9)

For a system that satisfies one of (8) or (9), a change in the result

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FR in the measurement process at variable temperatures is extremely small. The amplitudes of the oscillations of the load in the measuring circuit here are determined by possible deviations from conditions (8) or (9) arising due to possible errors in the manufacture of cells or selection of reference solutions, and when the temperature of the studied samples changes by tens of degrees lie within ± 0 , 1 g. This allows you to increase the resolution of the device up to 10% and create volumetric dilatometers of a qualitatively new level.

Thus, the proposed device eliminates the friction typical of conventional dilatometers in measurement and load systems, thereby preventing errors due to mechanical pastes and reducing the inertia of the instrument. It makes the process of measuring volumetric effects independent of the weight of the elements of the setup and the samples under study, which makes it possible to conduct bulk dilatometry under weightless conditions.

Claims (2)

1. A device for measuring volumetric 30 effects, containing working and reference cells with mounted inlays, connected with a loading mechanism and a system for recording the longitudinal deformation of these inserts, in order to extend the functionality of the device by ensuring its work in conditions of weightlessness, the loading mechanism is designed in the form of a screw rigidly connected with a chain of two elastic elements connected by a rod with a supporting disk fixed on it, with the end of the second pack ugogo member coupled to the bellows insertion reference cell, and the bellows insert working cell is connected through a recording system situated above the supporting, drive sleeve, which passes through an opening stock. 2. The device according to claim 1, characterized in that the effective cross-sectional areas of the bellows inserts in the working 5rab and reference 5e cells or the volumes of the working Vpa6 and reference VST cells and the stiffness coefficients Ki and K2 of the elastic elements are related by Spa6 UET K2 + KI Vpa6K2 five 79 20