SU446772A1 - Temperature measuring device - Google Patents

Description

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The invention relates to the field of thermometry and can be used as a reversible thermal indicator in temperature studies.

Temperature measurement devices are known based on the use of melting thermal indicators, which change their appearance abruptly when a certain temperature is reached and retain it with further temperature measurements.

The disadvantages of such devices are their irreversibility, and as a result of this one-time use, as well as the lack of accuracy (1-2 °) of temperature indication.

The purpose of the invention is to improve the accuracy of temperature measurements and ensure the possibility of multiple use of the device.

This is achieved by the fact that the proposed device is based on a nematic-cholesteric mixture, for example, a mixture of para-anisylidene-para-butylaniline and cholesteryl erucate, enclosed in a flat cell with an electrically conductive bottom, on a transparent lid of which is applied a transparent for white light electrically conductive coating, for example, tin oxides, and a low-frequency electric generator, such as 1500 Hz, 120 V, periodically connected to the bottom of the cuvette and the conductive coating, restoring the appearance (transparency) of the nematic cholesteric mixture.

FIG. 1 shows the proposed device before exposure to a critical temperature; in fig. 2 - the same, after exposure to the critical temperature.

Here: 1-cuvette, 2 - electrically conductive bottom of the cuvette, 3 - electrically conductive transparent coating applied to the lid of the cuvette,

4 - nematic cholesteric mixture, 5-- object under study, 6 - low frequency generator.

The device is made in the form of a flat cell with a transparent, for example glass,

lid and can have any shape. The thickness of the nematic-cholesteric mixture of 20-30 microns.

The device works as follows. Due to the similarity of the molecular structures of the nematic and cholesteric phases, the nematic phase imposes its cholesteric structure. In view of this, the mixture obtained is optically uniform over a wide temperature range. As the temperature rises, the temperature of the phase transition of the nematic phase (critical temperature) changes, its structure changes and its effect on the cholesterpical phase weakens. As a result, the cholesteric component is collapsed into large

conglomerates (droplets) are of the order of several wavelengths, and the mixture is transformed into an Uh-worm with suspended drops and becomes a scattering (milky-white) system.

As the temperature decreases, the nematic phase returns to its former structure, but its lattice energy is insufficient to destroy the large formations of the cholesteric phase.

To restore the transparency of the mixture, it is necessary to act on it with an electrical voltage of acoustic frequency, and the ions of the cholesteric phase begin to oscillate with the frequency of the electric field, which leads to the destruction of the cholesteric conglomerates. The mixture returns to its original state, i.e., becomes a white-transparent system.

As a nematic-cholesteric mixture, a composition containing a para-anisylidene-para — butylaniline (nematic phase) and cholesteryl erucate (cholesteric phase) can be used.

For a 25 μm blend layer, light scattering increases to about 200: 1 when the critical temperature is reached.

When the concentration of the cholesteric phase changes from 2 to 15%, the critical phase transition temperature in the range of -18 + 50 ° C changes.

Using different nematic-cholesteric mixtures, as well as changing their proportion within the same mixture, it is possible to fabricate temperature sensors for a wide range of critical temperatures.

When examining the temperature of an object with different critical temperatures, it is advisable to color the bottom of the cuvette of various sensors, respectively, in different colors that contrast with the color of the object under study. Then, before the phase transition through the transparent layer of the mixture, the color of the colored bottom of the cell is visible. After the phase transition, the clouded mixture masks the color of the bottom of the cuvette.

Subject invention

A temperature measuring device containing a material that changes appearance when a certain temperature is reached, characterized in that, in order to increase the temperature measurement accuracy and to ensure the possibility of multiple use of the device, a nematic-cholesteric mixture, such as a mixture of steam, is taken as a material. aniline-parabutylaniline and cholesteryl erucate enclosed in a flat cell with an electrically conductive bottom, on a transparent lid of which is applied a white transparent electric wire A low-frequency electrical generator is connected through a switch to the bottom of the cuvette and to the conductive coating.

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