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ITS-90 Reference Function Calculator
| Select one of the 12 ITS-90 fixed-points from the keypad, or type a temperature between 259.3467 °C (13.8033 K) and 961.78 °C (1234.93 K) into the Temperature window and press Calculate. The calculator will produce the ITS-90 reference function value Wr) and the sensitivity (dT/dW) for that temperature. Wr is a resistance ratio (RT90/RTPW) that represents the ideal behavior of platinum resistance thermometers that meet the ITS-90 definition. dT/dW describes the slope of the reference function at the selected temperature and can be used to calculate the impact of an incremental change in temperature on Wr.
ITS-90 fixed-point temperatures occur at the boundaries between solid, liquid, and vapor phases of matter. They include triple points (Tp), freezing points (Fp) and melting points (Mp). For example, the triple point of water (H20 Tp, or TPW) is the temperature (0.010 °C) where all three phases (solid, liquid, and vapor) are in equilibrium together. FpZn is the freezing point temperature (419.527 °C) where Zn makes a transition from liquid to solid. |
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