Temperature measurement

For instance in 170 AD, physician Claudius Galenus[1]: 18  mixed equal portions of ice and boiling water to create a "neutral" temperature standard.

This consists of a glass tube filled with mercury or some other liquid, which acts as the working fluid.

What thermal comfort humans, animals and plants experience is related to more than temperature shown on a glass thermometer.

Triple points are conditions of pressure, volume and temperature such that three phases are simultaneously present, for example solid, vapor and liquid.

For a single component there are no degrees of freedom at a triple point and any change in the three variables results in one or more of the phases vanishing from the cell.

Therefore, triple point cells can be used as universal references for temperature and pressure (see Gibbs phase rule).

In the study of the quark–gluon plasma through heavy-ion collisions, single particle spectra sometimes serve as a thermometer.

[2] In the field of reactive flows (e.g., combustion, plasmas), laser induced fluorescence (LIF), CARS, and laser absorption spectroscopy have been exploited to measure temperature inside engines, gas-turbines, shock-tubes, synthesis reactors[3] etc.

The American Society of Mechanical Engineers (ASME) has developed two separate and distinct standards on temperature Measurement, B40.200 and PTC 19.3.

Wildfires, volcanos, and industrial hot spots can also be found via thermal imaging from weather satellites.