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从1990年1月1日起,新的国际温标ITS-90正式开始实行,取代自1968年以来使用的国际实用温标IPTS-68,它的低温下限达到了0.65K。本文将介绍这一新温标的主要内容,并特别侧重于273.16K以下的温区。在国际温标—T_(90)中,0℃度以下温度的定义值与热力学温度之间的偏差温度在几个mK之内。新的温标简化了在14K以上温度使用铂阻温度计的过程。在3K到25K之间,ITS-90采用了内插气体温度计作为新标准,而在0.65K至5K之间则用~3He和~4He的蒸汽压来作标准。
From January 1, 1990 onwards, the new International Temperature Scale ITS-90 officially started to replace the international practical temperature gauge IPTS-68 since 1968, its low temperature limit reached 0.65K. This article will introduce the main contents of this new temperature scale, with particular emphasis on the 273.16K below the temperature zone. In the international temperature scale -T_ (90), the deviation between the defined value of the temperature below 0 ℃ and the thermodynamic temperature is within a few mK. The new temperature scale simplifies the use of platinum resistance thermometers at temperatures above 14K. Between 3K and 25K, the ITS-90 uses the interpolated gas thermometer as the new standard, while the vapor pressure of ~ 3He and ~ 4He is used as a standard between 0.65K and 5K.