What is the working principle of the temperature tester?
According to the purpose of use, a variety of thermometers have been designed and manufactured. The basis for its design are: the use of solids, liquids, and gases that are subject to thermal expansion and contraction under the influence of temperature; under constant volume conditions, the pressure of a gas (or vapor) varies with different temperatures; the role of thermoelectric effects; resistance varies with Changes in temperature; effects of heat radiation, etc.
The earliest thermometer was invented by Italian scientist Galileo (1564 ~ 1642) in 1593. His first thermometer was a glass tube with an open end and a large glass bulb on the other end. When using, first heat the glass bulb, and then insert the glass tube into the water. With the change of temperature, the water surface in the glass tube will move up and down. According to the amount of movement, you can determine the temperature change and the temperature level. Thermometers have the effects of thermal expansion and contraction. Therefore, this thermometer is greatly affected by environmental factors such as atmospheric pressure, so the measurement error is large.
Later, Galileo's students and other scientists repeatedly improved on this basis, such as turning the glass tube upside down, placing the liquid in the tube, and closing the glass tube. More prominent is the thermometer manufactured by the Frenchman Blioau in 1659. He reduced the volume of the glass bulb and changed the temperature measurement substance to mercury. This thermometer has the prototype of the current thermometer. Later, the Dutchman Wallenheit used alcohol in 1709 and in 1714 used mercury as a measuring substance to make a more accurate thermometer. He observed the boiling temperature of water, the temperature when water and ice were mixed, and the temperature when salt water and ice were mixed. After repeated experiments and approvals, the temperature of a certain concentration of salt water was set to 0 ° F. The temperature is set to 32 ° F, the temperature at which water boils at standard atmospheric pressure is set to 212 ° F, and Fahrenheit is used to represent Fahrenheit, which is the Fahrenheit thermometer.
At the same time as the appearance of the Fahrenheit thermometer, the Frenchman Lemuir (1683 ~ 1757) also designed and manufactured a thermometer. He believes that the expansion coefficient of mercury is too small to be suitable for temperature measurement. He focused on the advantages of using alcohol as a temperature-measuring substance. He repeatedly found that the volume expansion of alcohol containing 1/5 of water increased from 1000 volume units to 1080 volume units between the freezing temperature and the boiling temperature of water. Therefore, he divided the freezing point and boiling point into 80 parts, and set it as the temperature division of his thermometer. This is the Leh thermometer. ?
After more than 30 years after the Fahrenheit thermometer was made, the Swedish Celtics improved the scale of the Wallenheit thermometer in 1742. He set the boiling point of water to 100 degrees and the freezing point of water to 0 degrees. Later, his colleague Schlemmer reversed the values of the two temperature points and became the current percent temperature, which is expressed in degrees Celsius. The relationship between Fahrenheit and Celsius is ℉ = 9/5 ℃ + 32, or ℃ = 5/9 (℉ -32).
In Britain and the United States, Fahrenheit is now more commonly used, and Lehrs temperature is more commonly used in Germany. In the world's scientific and technological circles and industrial and agricultural production, as well as in China and France, most countries use Celsius.