Celsius
The degree Celsius is a unit of temperature.
Definition
The Celsius temperature is the thermodynamic temperature equivalent:
For the numerical values of a Celsius temperature and the corresponding thermodynamic temperature, the following relationship applies:
The curly brackets denote here only the numerical values , namely when using the units Celsius or Kelvin.
According to the rules of the institutions of international Metre Convention, however, the degree Celsius may also be used together with SI intentions, according to German law no unit. This provision was not included in the national German standardization of the German Institute for Standardization ( DIN 1301-1, DIN 1345 ).
By redefining the Celsius scale on the Kelvin scale, the melting and the boiling point of water are not exactly at 0 ° C and 100 ° C, but at 0.002519 ° C and 99.9839 ° C ( 99.9743 ° C according to ITS-90).
History
The Celsius scale goes back to the Swedish astronomer Anders Celsius, a wholly -piece temperature scale introduced in 1742. As fixed points he used, such as the 1730 presented Reaumur scale, the temperatures of freezing and boiling point of water at atmospheric pressure, that is an air pressure of 1013.25 hPa or 760 millimeters of mercury. The range between these fixed points, measured with a mercury thermometer, is divided into 100 equal time intervals, which are referred to as degrees. This led to the historic designation of the " centigrade thermometer ". Unlike the modern Celsius scale, however the boiling point of water disposed Celsius to 0 ° C and the freezing point to the value of 100 °. Thus, the value of a body temperature decreased during heating.
The modern Celsius scale, in which the boiling point of water, the value of 100 ° and the freezing point of 0 ° is assigned, was Carl Linnaeus, a friend Celsius ', introduced shortly after his death in 1744.
1948, about 200 years after the introduction of the scale, was officially renamed in honor Celsius ' scale of distance in a Celsius thermometer centigrade or by a Zentesimalgrad through the 9th International General Conference on Weights and Measures in the temperature unit degree Celsius.
Another definition is the standard DIN 1345 (December 1993) of the DIN basis. It is introduced a special size designation "Celsius temperature". This is the difference of the respective thermodynamic temperature and a fixed reference temperature 273.15 Kelvin ( unit symbol K ). Because this standard for temperature differences using the Kelvin recommends that it continues to give that ": used as a special name for the kelvin When specifying the Celsius temperature of the unit name degrees Celsius (° C Unit characters). "
Symbols for thermodynamic temperature and Celsius temperature
As a symbol for the Celsius temperature is the (to differentiate also ) ( theta) and DIN 1345 of December 1993, the small t common and standard; incorrectly, however, the large T is used for this purpose. Actually, T is the absolute temperature in Kelvin reserved.
Temperature difference
The temperature difference is the difference in the temperature of two measuring points which are different in the time or spatial position.
As a unit of temperature differences is with the standard DIN 1345 (December 1993) the Kelvin recommended by DIN in adaptation to the SI system. The DIN added to " Following the decision of the 13th General Conference on Weights and Measures ( 1967-1968 ) may be given the difference of two Celsius temperatures, in degrees Celsius (° C). " For the purposes of this standard, the "Celsius temperature " the difference of the respective thermodynamic temperature and the fixed reference temperature is 273.15 K; when specifying the Celsius temperature of the unit name degrees Celsius is used as a special name for the kelvin ( because of temperature differences the standard recommends yes on the Kelvin).
The numerical values of temperature differences agree with the use of the units Kelvin and Celsius match:
Conversion
In the following section, some conversion tables for different temperature values and units are given.