temperature is hot and cold characterization of the degree of physical objects. Temperature only through objects with temperature changes in the characteristics of some of the indirect measurement, and the objects used to measure the temperature scale called the numerical temperature scale. It provides temperature readings starting point (zero) and the basic unit of measurement of temperature. At present, more use of the temperature scale Fahrenheit temperature scale there, Celsius temperature scale, thermodynamic temperature scale and international practical temperature scale.
Fahrenheit temperature scale (oF): In the standard atmospheric pressure, the ice melting point of 32 degrees, the boiling point of water for the 212, 180 sub-divided in the middle of each section is divided into a newspaper's degree, symbols For oF.
Celsius ( ): In the standard atmospheric pressure, the ice melting point is 0 degrees, the boiling point of water is 100 degrees, 100 sub-divided in the middle of each section is divided into a newspaper's degrees, for the symbol .
thermodynamic temperature scale, also known as Kelvin temperature scale, or absolute temperature scale, it provides elements of the campaign to stop when the temperature of absolute zero, remember to sign K.
international practical temperature scale is an international agreement of temperature scale, with its thermodynamic temperature scale similarity to the current complex and high precision, easy to use. At present, the international temperature scale is the 1975 15th International General Assembly adopted the right time "in 1968 international practical temperature scale -1975 Revision," to remember: IPTS-68 (Rev-75). However, Wen said IPTS-68 There is a certain lack of metering of the International Committee of 18 in the seventh session of the General Assembly of the International Measurement resolution to authorize the 1989 session in 1990 adopted the International Temperature Scale ITS-90, ITS-90 temperature scale alternative IPTS-68. Since January 1, 1994 from the full implementation of ITS-90 international temperature scale.
1990 of the International Temperature Scale (ITS-90) Following is a brief introduction.
1. Temperature unit
thermodynamic temperature (as a symbol T) is a basic physics hands, and its units Kelvin (as a symbol K), defined as the point of the three-phase water temperature thermodynamics 1/273.16. As the previous definition of the temperature scale, with the use of 273.15K (freezing point) to indicate the temperature difference, so it is still the method.
by definition, equal to the size of degrees Kelvin, the temperature difference can also be used degrees Kelvin, or expressed.
international temperature scale ITS-90 at the same time the international definition of Kelvin temperature (symbol for the T90) and the International Celsius (symbol for t90)
2. International Temperature Scale of ITS-90 General
ITS-90 from 0.65K up to the Planck radiation law of the use of monochromatic radiation actual measurable maximum temperature. ITS-90 is formulated this way, that is, in the whole range, the T90 temperature of any value is very close to T when the temperature scale adoption of best estimate, and compared to the direct measurement of thermodynamic temperature, T90 measurement to be much more convenient and more For the precision and high reproducibility.
3. ITS-90 definition of
temperature for the first 0.65K to 5.00K between, T90 by 3He 4He and the vapor pressure and temperature to define the relationship.
second temperature 3.0K for the three-phase to the point of neon (24.5661K) between the T90 with helium Gas thermometer to define.
temperature for the second three-phase hydrogen balance point (13.8033K) to the freezing point of silver (961.78 ) between, T90 by the PRT to the definition. It uses a set of provisions of the definition and use of a fixed point within the provisions of Interpolation to indexing.
silver freezing point (961.78 ) over the temperature, T90 is based on Planck's radiation law to define, are complex instruments for the optical pyrometer
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Pressure detection and transmission
Testing instrument with the temperature