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Temperature Standard

The unit of thermodynamic temperature (kelvin) is defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
However, due to the measuring complexities involved, a scale which indicates thermodynamic temperature accurately to one or two degrees, was adopted internationally.
The temperature scale has been revised several times, and the International Scale of 1990 (ITS) is currently used.

Triple point cell of water

The International Temperature Scale of 1990(ITS-90)



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