There are a wide variety of temperature measurement probes in use today depending on what you are trying to measure, how accurately you need to measure it, if you need to use it for control or just man monitoring, or if you can even touch what you are trying to monitor.
Temperature measurement can be classified into a few general categories:
Thermometers are the oldest of the group. The need to measure and quantify the temperature of something started around 150 A.D. when Galen determined the ‘complexion’ of someone based on four observable quantities.
The actual science of ‘thermometry’ did not evolve until the growth of the sciences in the 1500’s The first actual thermometer was an air-thermoscope described in Natural Magic (1558, 1589). This device was the fore runner of the current class of glass thermometers. Up to 1841 there were 18 different temperature scales in use.
An instrument maker, Daniel Gabriel Fahrenheit learned to calibrate thermometers from Ole Romer, a Danish astronomer. Between 1708 and 1724 Fahrenheit began producing thermometers using Romer’s scale and then modified that to what we know to day as the Fahrenheit scale.
Fahrenheit greatly improved the thermometer by changing the reservoir to a cylinder and replaced the spirits used in the early devices with mercury. This was done because it had a nearly linear rate of thermal expansion.
His calibration techniques were a trade secret, but it was known that he used a certain mixture of the melting point of a mixture of sea salt, ice and water and the armpit temperature of a healthy man as calibration points. When the scale was adopted by Great Britain the temperature of 212 was defined as the boiling point of water. This point as well as the melting point of plain ice were used as two known calibration points.
About 1740 Anders Celsius proposed the centigrade scale. It is not clear who invented the scale, but it divided the range of the melting point of ice (100) to the steam point of water (0) into 100 parts, hence ‘centigrade’. Linnaeus inverted the scale so that 0 was the ice point and 100 was the steam point. In 1948 the name of the centigrade scale was changed to Celsius.
About the time that Fahrenheit was experimenting with his liquid filled devices, Jaspeh L. Gay-Lussac was working with gas filled tubes. He concluded that at a constant pressure, the volume of the gas would expand at a particular rate for each degree of temperature rise, that being 1/267 per degree.
In 1874 Victor Regnault obtained better experimental results, showing this number to be 1/273 and concluded that the pressure would approach zero at 1/273.15 degrees C. This lead to the definition of zero pressure at -273.15 degrees C, or what we now know as the absolute scale.