thermometers

The thermometers, is temperature-measuring device's general name, may the accurate judgment and the survey temperature. The earliest thermometer was (1564~1642) invents in 1593 by Italian scientist Galileo. His first thermometer is an end opens the mouth the glass tube, another end has the walnut big glass bulb. When use heats up first to the glass bulb, then glass tube insertion water. Along with the temperature change, in glass tube's water surface will reciprocate that may determine the temperature according to motion how many change and the temperature height. The thermometer has the expand with heat and contract with cold function, therefore this kind of thermometer, environmental factor's and so on outside the atmosphere intensity of pressure influences is been big, therefore the measuring error is big, the measuring accuracy is not very ideal. Afterward Galileo's student and other scientists, improved repeatedly in this foundation, like the glass tube in reverse, placed the liquid in the tube, glass tube seal and so on. What compared with is prominent is French cloth Leo the thermometer which made in 1659, he glass bulb's volume reduction, and changed the temperature measurement material the mercury, such thermometer has had the present thermometer's embryonic form. Afterward German Holland physicist Warren Hiter when 1709 has invented the alcohol thermometer, when 1714 uses the mercury to replace the ethyl alcohol, takes the survey material the mercury, has made a more precise thermometer, thus caused the thermometer to make the crucial progress. He observed the water boiling heat, Shui Hebing time time the mix temperature, the salt water and the ice mix temperature; After tests repeatedly with approves, finally decides as time certain density's salt water coagulation's temperature 0℉, decides as the pure water coagulation's time temperature 32℉, decides as the standard atmospheric pressure sewer ebullition's temperature 212℉, with ℉ represents the fahrenheit, this is the fahrenheit thermometer. 　　

 Now thermometer's type are many, mainly has the petroleum thermometer, the alcohol thermometer, the mercury thermometer, the gas thermometer, the resistance thermometer, the thermo couple thermometer, the solar thermometer and the flash ranging thermometer, the bimetallic thermometer. Although the variety are many, but in the principle basic is consistent, many are using the solid, the liquid, the gas the temperature influence, but expand with heat and contract with cold's phenomenon designs. But along with the technical progress basis use goal's difference, has more and more thermometers to make. Its design's basis has, primitive: Using solid, liquid, gas temperature influence, but expand with heat and contract with cold phenomenon; Constant volume condition: Gas (or vapor) temperature change initiation intensity of pressure change; Pyroelectric effect function: The resistance changes along with the temperature change; Heat radiation influences and so on. In general, all material any physical property, so long as it has monotonously, the remarkable change along with the temperature change, may use for to symbolize that the temperature makes the thermometer. Below introduced in detail in the current society uses the quite widespread several kind of thermometers.

1st, gas thermometer: The multipurpose hydrogen or the helium make the temperature measurement material, because the hydrogen and the helium liquefaction temperature is very low, approaches in the zero absolute temperature, therefore its temperature measurement scope is very broad. This kind of thermometer precision is very high, uses in the precision measurement. 　　

2nd, resistance thermometer: Divides into the metal resistance thermometer and the semiconductor resistance thermometer, is makes according to the resistance value along with temperature change this characteristic. Fine metal and rhodium iron, phosphor bronze alloy and so on metallic thermometer main useful platinum, gold, copper, nickel; The semiconductor thermometer mainly uses the carbon, the germanium and so on. The resistance thermometer easy to operate is reliable, has widely applied. Its measuring range for - 260℃ to 600℃ about. 　　

 3rd, thermo couple thermometer: Is in one industry the widespread application temperature-measuring device. Makes using the thermoelectric phenomenon. Two kind of different tinsel weld are forming the working end together, another both sides and the measuring instrument connection, forms the electric circuit. Places the working end is measured the temperature place, when the working end and the free electricity temperature is different, will present the electromotive force, will thus have the electric current to adopt the return route. Through the electricity quantity's survey, the use known place temperature, may determine another temperature. It is suitable between the temperature difference big two materials, uses in the high temperature and the low muddy survey. Some thermo couple can survey reaches as high as 3000℃ the high temperature, some can measure the close zero absolute temperature the low temperature. 　　

4th, high-reading thermometer: Is refers to uses for to survey 500℃ the above temperature thermometer specially, has the flash ranging thermometer, the color temperature to count with the solar thermometer. High-reading thermometer's principle and the structure are quite complex, here no longer discusses. Its measuring range for 500℃ to 3000℃ above, is not suitable for the survey low temperature. 　　

5th, indicator type thermometer: Is the shape according to dial plate's thermometer, also calls the thermometer, uses for to measure the room temperature, is makes with the metal expand with heat and contract with cold principle. It does take the bimetal piece as the bulb, uses for the steering needle. The bimetal piece usually is with the sheet copper and the iron sheet riveting in the same place, and sheet copper in left, iron sheet in right. As a result of the copper expand with heat and contract with cold effect must many which is more obvious than the iron, therefore works as when temperature increment, the sheet copper pulls pulls the iron sheet to be toward right curving, under the indicator in the bimetal piece leads toward right deflects (directional high temperature); Otherwise, the temperature changes low, under the indicator in the bimetal piece leads toward left deflects (directional low temperature). 　

6th, glass tube thermometer: The glass tube thermometer is realizes the temperature survey using the expand with heat and contract with cold principle. As a result of temperature measurement medium expansion coefficient and boiling point and solidification point difference, therefore our common glass tube thermometer mainly has: Petroleum thermometer, mercury thermometer, red ink thermometer. His merit is the structure is simple, the easy to operate, the measuring accuracy is relatively high, low in price. The shortcoming is surveys the bound and the precision the glass quality and the temperature measurement medium nature limit. And cannot the long-distance range transportation, brittle. 　　

 7th, pressure thermometer: The pressure thermometer is uses in the seal vessel's liquid, after the gas either the saturated steam heating, has the volume expansion or the pressure variation achievement measures the signal. Its basic structure is by the temperature bulb, the capillary vessel and the dial gage three parts is composed. The pressure thermometer's merit is the structure is simple, the mechanical strength is high, does not fear the vibration. The low in price, does not need exterior energy. The shortcoming is the temperature measurement scope has the limit, generally in - 80~400℃; The heat los big response time is slow. 　　

8th, mercury thermometer: The mercury thermometer is the inflation type thermometer's one kind, the mercury solidification point is: - 38.87℃, the boiling point is: 356.7℃, uses for to survey 0--150℃ or 500℃ within the scope temperature, it can only take on-the-spot surveillance the measuring appliance. Surveys the temperature with it, not only quite simple direct-viewing, moreover exterior may also avoid the far biography thermometer's error.

 From above each kind of thermometer introduced that I believed may at least has a basic understanding to the nowadays existence various types thermometer type as well as their temperature measurement principle. But along with the science gradual progress, I believed that also will have a more advanced thermometer to appear on the market one after another, everybody may anticipate that one day-long arrival.