主要溫度標準

• 純度高，不確定度極低
• 多種尺寸，多種選擇
• 優異的同位素水平
• 特殊應用的小型水三相點

水三相點（TPW）是唯一一個同時被熱力學溫標和國際溫標定義的溫度固定點。熱力學溫度的單位，開爾文，被定義為水三相點熱力學溫度的1/273.16。

它也是1990年國際溫標（ITS-90）的定義固定點。因此水三相點溫度是易於使用的溫度標準。

福祿克的水三相點瓶以小於0.0001℃的擴展不確定度實現0.01℃溫度。如果您擁有標準鉑電阻溫度計SPRT，就必須要有一個高質量的水三相點瓶。

Must-have, primary temperature standards

• Easy-to-use, inexpensive standard with uncertainty better than ± 0.0001 °C
• Four sizes and two shells (glass and quartz) to choose from
• Isotopic composition of Vienna Standard Mean Ocean Water

The triple point of water (TPW) is not only the most accurate and fundamental temperature standard available, it’s also one of the least expensive and simplest to use.

Water cells are essential!

Triple point of water cells fill four critical purposes. First, they provide the most reliable way to identify unacceptable thermometer drift between calibrations—including immediately after a calibration if the thermometer has been shipped. Interim checks are critical for maintaining confidence in thermometer readings between calibrations. Second, they provide a critical calibration point with unequaled uncertainties.

Third, for users who characterize probes using ratios (that is, they use the ratios of the resistances at various ITS-90 fixed points to the resistance of the thermometer at the triple point of water, indicated by “W"), interim checks at the triple point of water allow for quick and easy updates to the characterizations of critical thermometer standards, which can be used to extend calibration intervals.

And lastly, the triple point of water is where the practical temperature scale (ITS-90) and the thermodynamic temperature scale meet, since the triple point of water is assigned the value 273.16 K (0.01 °C) by the ITS-90 and the Kelvin is defined as 1/273.16 of the thermodynamic temperature of the triple point of water.

Good triple point of water cells contain only pure water and pure water vapor. (There is almost no residual air left in them.) When a portion of the water is frozen correctly and water coexists within the cell in its three phases, the “triple point of water" is realized. Fluke Calibration water cells achieve this temperature with expanded uncertainties of less than 0.0001 °C and reproducibilities within 0.00002 °C.

In simple terms, water cells are made from just glass and water, but there’s much more to it than that!

For starters, that’s not just any water in there.