Editing Thermometer (section)

==Primary and secondary thermometers==
A thermometer is called primary or secondary based on how the raw physical quantity it measures is mapped to a temperature. As summarized by Kauppinen et al., "For '''primary thermometers''' the measured property of matter is known so well that temperature can be calculated without any unknown quantities. Examples of these are thermometers based on the equation of state of a gas, on the [[velocity]] of sound in a gas, on the [[Johnson–Nyquist noise|thermal noise]] [[voltage]] or [[electric current|current]] of an electrical resistor, and on the angular [[anisotropy]] of [[gamma ray]] emission of certain [[radioactive decay|radioactive]] [[atomic nucleus|nuclei]] in a [[magnetic field]]."<ref name="kauppinen1998">{{Cite journal | last1 = Kauppinen | first1 = J. P. | last2 = Loberg | first2 = K. T. | last3 = Manninen | first3 = A. J. | last4 = Pekola | first4 = J. P. | doi = 10.1063/1.1149265 | title = Coulomb blockade thermometer: Tests and instrumentation | journal = Rev. Sci. Instrum. | volume = 69 | issue = 12 | pages = 4166–4175 | year = 1998 |bibcode = 1998RScI...69.4166K | s2cid = 33345808 | doi-access = free }}</ref>

In contrast, "Secondary thermometers are most widely used because of their convenience. Also, they are often much more sensitive than primary ones. For secondary thermometers knowledge of the measured property is not sufficient to allow direct calculation of temperature. They have to be calibrated against a primary thermometer at least at one temperature or at a number of fixed temperatures. Such fixed points, for example, [[triple point]]s and [[Superconductivity|superconducting]] transitions, occur reproducibly at the same temperature."<ref name="kauppinen1998"/>