A cryometer is a

thermometer A thermometer is a device that measures temperature or a temperature gradient (the degree of hotness or coldness of an object). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermomete ...

used to measure very low temperatures of objects. Ethanol-filled thermometers are used in preference to mercury for meteorological measurements of minimum temperatures and can be used down to −70 °C (-94 °F). The physical limitation of the ability of a thermometer to measure low temperature is the freezing point of the liquid used. There are many types of devices used as cryometers: #

thermocouples A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the ...

: these can be used down to measure about 1 K temperature. #

vapour pressure thermometer A vapour pressure thermometer is a thermometer that uses a pressure gauge to measure the vapour pressure Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pre ...

s: these can be used to measure temperatures down to about 0.5K #

resistance thermometers Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. Many RTD elements consist of a length of fine wire wrapped around a heat-resistant ceramic or glass core but other constructio ...

: these can be used to measure temperatures at 0.01 K. #

melting curve thermometer Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which incre ...

s: these can be used to measure temperatures between about 0.001K and 0.5K #

resistance noise thermometer Resistance may refer to: Arts, entertainment, and media Comics * Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm: ** ''Resistance'' (comics), based on the video game of the same title ** ''T ...

s: these can be used to down to about 0.001K #

magnetic thermometers Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...

: which are used at 0.001 K temperatures. # nuclear-resonance thermometers: these are required to measure very low temperatures such as 0.0000001 K.

References

*Oxford dictionary of science, 1999, 4th edition, . Thermometers {{Thermodynamics-stub