What is a fixed point? How many of them are there?
Written by Olivia
/ Reading time - 1 min
Partager
The ITS (International Temperature Scale) uses 17 temperature reference points based on the physical phenomenon of the triple point, the vapour pressure, the freezing point, melting point and solidification point of different substances. These distinct points occur at a fixed, reproducible temperature, determined by nature. They do not require the use of a reference sensor in order to measure them. For example, gallium always melts (goes from solid state to liquid state) at 29.7646°C. A distinct fixed point is the triple point. And a distinct triple point is the triple point of water (0.01°C under 1 atm).
The triple point is the point at which the vaporisation curve, the sublimation curve and the fusion curve of a substance meet. It was Josiah W. Gibbs (1839-1903) who recognised and proposed the phase rule: the three states, solid, liquid, gas, only coexist at one unique point within the thermodynamic parameters, the triple point. Vapour, liquid and solid are found together at a unique defined temperature and pressure.
Figure 1. Change in pressure with temperature for the triple point of water
Our latest articles
Reading time - 5 min
Upcoming events
Book following dates in your calendar: M+R 2025 – from 03/26/2025 to 03/27/2025 – Antwerp Expo – Stand 3100, Come and visit us! Invitation : https://register.visitcloud.com/survey/22v8m6mjp0fa5?actioncode=NTWO000049WQL&partner-contact=0esxkhcpph1iu…
Why is temperature not a physical quantity like other measurement units?
Temperature is not a quantity in the strict sense of the term as the majority of other measurement units are. A quantity is something which can be increased or decreased, for example length, area, power output, etc. Measuring a quantity…
Inor : Product Launch: Innovative Field Housing and Smart Indicators
Inor is excited to introduce our brand-new field housing and indicators, designed to deliver a reliable solution in demanding environments. These products combine robust construction with practical features to ensure long-term use, even in the most challenging conditions.
Beamex: Calibration Excellence since 1975 🏆
Beamex celebrates 50 years of providing the Process Industry with a better way to calibrateMore info Here
Thermibel goes social! 🎉
We’re delighted to announce that we’ve reached a new milestone! 📲You can now follow all our news, tips, innovations and meet our team directly on your favorite platforms. Follow us on our social networks! 🌟 📘 Facebook: https://www.facebook.com/profile.php?id=61563829479501…