it is an equipment calibration standard. Temperatures measured with equipment calibrated per ITS-90 may be expressed using any temperature scale such as Celsius, Kelvin, Fahrenheit, or Rankine. For example, a temperature can be measured using equipment calibrated to the kelvin-based ITS-90 standard, and that value may then be converted to, and expressed as, a value on the Fahrenheit scale (e.g. 211.953 °F). ITS-90 does not address the highly specialized equipment and procedures used for measuring temperatures extremely close to absolute zero. For instance, to measure temperatures in the nanokelvin range (billionths of a kelvin), scientists using optical lattice laser equipment to adiabatically cool atoms, turn off the entrapment lasers and simply measure how far the atoms drift over time to measure their temperature. A cesium atom with a velocity of 7 mm/s is equivalent to a temperature of about 700 nK (which was a record cold temperature achieved by the NIST in 1994). Estimates of the differences between thermodynamic temperature and the ITS-90 () were published in 2010. It had become apparent that ITS-90 deviated considerably from PLTS-2000 in the overlapping range of 0.65 K to 2 K. To address this, a new 3He vapor pressure scale was adopted, known as . For higher temperatures, expected values for are below 0.1 mK for temperatures 4.2 K – 8 K, up to 8 mK at temperatures close to 130 K, to 0.1 mK at the triple point of water (273.1600 K), but rising again to 10 mK at temperatures close to 430 K, and reaching 46 mK at temperatures close to 1150 K. Standard interpolating thermometers and their ranges Defining points The table below lists the defining fixed points of the ITS-90. See also Thermodynamic (absolute) temperature — the "true temperature" which ITS-90 is attempting to approximate. Provisional Low Temperature Scale of 2000 (PLTS-2000) — A newer temperature scale for the range of 0.0009 K to 1 K, based on the melting pressure of helium-3. Kelvin Triple point Vienna Standard Mean Ocean Water (VSMOW) Resistance thermometer Platinum resistance thermometer Planckian locus § International Temperature Scale – how successive revisions of the temperature scale have affected the relation between spectrum and temperature of a black body References Preston-Thomas H., Metrologia, 1990, 27(1), 3-10 (amended version). External links The Internet ITS-90 Resource (by ISOTech Ltd) ITS-90 (by Swedish National Testing and Research Institute) About Temperature Sensors (information repository) NIST ITS-90 Thermocouple Database (by