Well - with, than we will take temperature?
“Thermometer, certainly!“ - you will answer, meaning the mercury or spirit thermometer. But modern idea of thermometers is much broader.
The thermometer in general call the device taking temperature at direct contact with the studied environment. Its action is based on change of any physical properties of substance.
Thermometers liquid, bimetallic, manometrical, resistance, thermoelectric are most widespread.
For contactless measurements (i.e. remote) other class of devices - pyrometers is created. These are the optical devices determining environment temperature by its radiation or absorption.
the Most ancient thermometerLong time of people used
only the “built-in thermometers“. On one square centimeter of a surface of his body 12 - 15 receptors of cold and 1 - 2 receptor of heat are located. (The general surface of a body makes one and a half - two square meters, or 15 000 - 20 000 sq. cm).
It is necessary to add to it also internal receptors. We feel what food we consume: cold or hot. We feel language, teeth, a gullet, a stomach … Medieval scientists judged
the taken temperature on the feelings too. But for a greater sciolism invented a special temperature scale. And on it three divisions: hotly, warmly, cold.
To judge the accuracy of such scale, you can make simple experiment. Take hands a couple of minutes in water: one - in cold, another - in hot. Then lower both in warm water. What “will“ they “tell“ you about temperature?
Oh this Galilei!
Galileo Galilei before creating the telescope and thoroughly to salt Inquisitions, it was warmed on trifles. As a result also the first-ever liquid thermometer appeared. According to modern and very inconsistent data, it happened in 1592 … 1597.
Galilei`s idea became similarity of the bone thrown into crowd of the yearned scientists. And what they with it only did not get up! And the design was remade. And liquids shuffled. And the scale was overturned. And zero on it was moved... Four were the most zealous: Fahrenheit, Reaumur, Celsius and Calvin.
of Feature of the liquid thermometer
use thermometers with Calvin`s scale to scientific researches Presently. In other cases the scale of Celsius or the Fahrenheit scale is used (in the USA).
Operation of the liquid thermometer is based on expansion of liquid at its heating. Range of the taken temperatures depends on the concrete liquid filling the thermometer. More precisely, from temperature of its hardening (melting) and from temperature of its boiling.
Proceeding from requirements, the thermometer fill with a pentane (-200 … +20 about C), ethyl alcohol (-80 … +70 about C), kerosene (-20 … +300 about C), mercury (-35 … +750 about C), etc.
the Most widespread are mercury thermometers as have the widest working range. With a normal pressure in the thermometer range begins at -35 about With and comes to an end at +356 about Page. If to create small excessive pressure, having filled a capillary with nitrogen, then the upper bound of working capacity is removed to +750 about S. Rtut - the only metal, liquid at the room temperature. Lower than temperature of melting (-38,9 about C) stiffen, forming malleable viscous weight.
As before, in a systemThough are created by
all new types of thermometers now, liquid still in a system and hold a leading position. It is promoted:
- simplicity of their design;
- autonomy - they do not depend on an external power source as, for example, thermoresistors;
- big range of measurement (-200 … +750 about C), covering as temperature of liquid oxygen (boils at -182,97 about C), and temperature of melting of many metals, for example, aluminum (melts at 660 about C).
Refer their considerable thermal inertia and dimensions to shortcomings of liquid thermometers, not always convenient in work.
Using these devices in life and on production, we with gratitude take off a hat before their creators.