The origins of some branches of science can hardly be traced. How, for example, you can determine: who was the first astronomer or mathematician. To such areas of human knowledge can be attributed probably meteorology. The weather could not help but interest the person, especially in the antediluvian times, when he was much less protected from natural disasters. Temperature is one of the basic characteristics of weather.
What is the temperature for?
We are used to measuring the temperature both inside and outside the dwelling, we usually look at the thermometer outside the window in the morning before leaving the house, taking care of the question of whether to wear a scarf and gloves. An alcohol, mercury, bimetallic thermometer outside the window is a familiar pattern for most citizens. Without measuring body temperature, there is almost no one medical examination.
But meteorologists are interested in the air temperature not only from the point of view of the effect on our skin. On how warmed up those or other layers of the atmosphere, the formation of air currents, winds, which form the weather of the continents, depends.
Temperature measurement in production is generally a separate topic. Such processes as cracking, polymerization, crystallization and thousands of other chemical and physical phenomena used in plants and factories proceed at a clearly defined temperature and pressure. And sometimes it takes an accuracy of a tenth of a degree. And in this case, traditional thermometers, using the effect of expanding bodies with heating, are quite difficult to apply. This is especially true when working in ultra-low temperatures, when most liquids lose their fluidity. And then often comes to the rescue thermometer bimetallic - TB, as it is customary to write abbreviated.
How did you learn to measure the temperature?
The inventor of the thermometer is reliably unknown. Some researchers attribute this merit to the great Galileo. The device for measuring the temperature, created by him, used compression-expansion of air. Even the scale instrument (called its thermoscope) did not have. With his help, watching the movement of the boundary of the air pushed out by the air, one could only determine whether the temperature is rising or falling. The accuracy of such a device left, to put it mildly, to be desired: its work was significantly influenced by atmospheric pressure, besides the boundary of water and air, both the saturation of air with water vapor and the dissolution of air in water, constantly "knocked down" the adjustment.
Later, as a working fluid, liquids with a significant coefficient of thermal expansion began to be used. The thermometers of steel became much more precise, the dimensions of the structure decreased to acceptable ones and this device slowly began to become massive.
As working fluids in such thermometers, mercury, various alcohols and even kerosene are used.
Other more modern and progressive methods of measuring temperature are methods based on electricity. It is known that all conductive materials change the resistance as a function of temperature. The soldering of some different metals with heating (thermoelectric steam) generates an electric current. These and other physical and chemical phenomena formed the basis for the means for measuring temperature.
A bimetallic thermometer, like a liquid one, uses the effect of expanding bodies when heated. Only in the quality of the working fluid is not used liquids or gases, but solid objects.
Let's consider its principle of action. We take two plates of different materials with different coefficients of thermal expansion.
At a temperature T1, the dimensions of the plates will be equal. But with the rise in temperature (up to T2) it is obvious that the product, which is made of a material with a large coefficient of expansion, will increase more. This is the case if both plates are by themselves. But it is worthwhile to combine these two plates (riveting, soldering, hot pressing, etc.), as the picture will change.
The different values of the interconnected plates (Δa \u0026 lt; Δb) force the entire structure to bend. And the bulge will appear from the side of the material with a large coefficient of expansion. Using this simple effect and working bimetallic thermometer. The bend value indicates the ambient temperature. In different designs, only the methods of measuring this bend differ.
What qualities distinguish a bimetallic thermometer from its counterparts?
- A liquid in a glass vessel is in itself a danger, especially if it is mercury, it is obvious that the bimetallic design is free of this drawback.
- Another such system does not need thermoelectric thermometers in power supply and additional equipment, which makes it more mobile and more convenient to use.
- The expansion of liquids under the effect of temperature is uneven, because their readings are not always correct, such a disadvantage does not suffer from a bimetallic thermometer radial.
In its design, a plate is used, twisted into a spiral. Due to the long working fluid temperature measurement is very accurate.
The German company Wika is a recognized leader in the production of temperature and pressure measuring instruments. Specialists of the company did not accidentally pay attention to the effect of changing the geometry of bimetallic plates. It must be said that in the manufacture of such means of measuring temperature, the firm has reached perfection. The thermometer bimetallic Wika is produced both in household version and in special versions. The main consumers of Wika products are companies engaged in heating networks and boiler equipment.
Thanks to the use of advanced technical solutions in production, careful selection of the highest quality materials, Wika products are successfully sold in more than one hundred countries of the world.