At extremely rare intervals the thermometer has fallen below zero (- 18 ° C ), as was the case in the remarkable cold wave of the 12th-13 February 1899, when an absolute minimum of-17 ° F (- 29 ° C ) was registered at Valley Head.

The question whether there is a limit to the degree of cold possible, and, if so, where the zero must be placed, was first addressed by the French physicist Guillaume Amontons in 1702, in connection with his improvements in the air thermometer.

Amontons therefore argued that the zero of his thermometer would be that temperature at which the spring of the air in it was reduced to nothing.

For years it was simply referred to as the Swedish thermometer.

Daniel Gabriel Fahrenheit ( 24 May 1686 – 16 September 1736 ) was a Dutch-German-Polish physicist, engineer, and glass blower who is best known for inventing the alcohol thermometer ( 1709 ) and the mercury thermometer ( 1714 ), and for developing a temperature scale now named after him.

The thermometer then was placed into the mixture and the liquid in the thermometer allowed to descend to its lowest point.

The second reference point was selected as the reading of the thermometer when it was placed in still water when ice was just forming on the surface.

" When Groucho himself was on his deathbed, and a nurse came around with a thermometer, explaining that she wanted to see if he had a temperature, he responded, " Don't be silly — everybody has a temperature.

The thermometer was not a single invention, however, but a development.

The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani: the first showing a scale and thus constituting a thermometer was by Robert Fludd in 1638.

However, each inventor and each thermometer was unique — there was no standard scale.

That is, the thermometer did not hold the temperature after it was moved to a place with a different temperature.

If the non-registering thermometer was removed from the hot liquid, then the temperature indicated on the thermometer would immediately begin changing to reflect the temperature of its new conditions ( in this case, the air temperature ).

The first registering thermometer was designed and built by James Six in 1782, and the design, known as Six's thermometer is still in wide use today.

The traditional method of putting a scale on a liquid-in-glass or liquid-in-metal thermometer was in three stages:

Temperature, as measured by an accurate, well calibrated thermometer, is empirical evidence.

They have to be calibrated against a primary thermometer at least at one temperature or at a number of fixed temperatures.

Nowadays manufacturers will often use a thermostat bath or solid block where the temperature is held constant relative to a calibrated thermometer.

Most thermometers are originally calibrated to a constant-volume gas thermometer.

Thus if the same type of thermometer is calibrated in the same way its readings will be valid even if it is slightly inaccurate compared to the absolute scale.

An example of a reference thermometer used to check others to industrial standards would be a platinum resistance thermometer with a digital display to 0. 1 ° C ( its precision ) which has been calibrated at 5 points against national standards (− 18, 0, 40, 70, 100 ° C ) and which is certified to an accuracy of ± 0. 2 ° C.

" ( Condorcet 1791 ) Four objects used in making measurements in everyday situations that have metric calibrations are shown: a tape measure calibrated in centimetre s, a thermometer calibrated in Celsius | degrees Celsius, a kilogram weight, and an electrical multimeter which measures volt s, ampere | amps and ohm s.

For example, a thermometer could be calibrated so the error of indication or the correction is determined, and adjusted ( e. g. via calibration constants ) so that it shows the true temperature in Celsius at specific points on the scale.

For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube.

Griddle thermostats should be calibrated by a trained professional with the appropriate equipment-a high-quality digital surface thermometer is critical, and the process should be performed to the manufacturer ’ s specifications.

He then sent this calibrated thermometer to various scholars, including Anders Celsius.

Between 3. 0 K and 24. 5561 K ( triple point of neon ) ITS-90 is defined by means of a helium gas thermometer calibrated at three fixed points in this range.

Between 13. 8033 K ( triple point of equilibrium hydrogen ) and 1234. 93 K ( freezing point of silver ) ITS-90 is defined by means of a Standard Platinum resistance thermometer ( RTD ) calibrated at the defining fixed points and using specified interpolation procedures.

Such thermometers are usually calibrated so that one can read the temperature simply by observing the level of the fluid in the thermometer.

A thermometer has two important elements: the temperature sensor ( e. g. the bulb on a mercury thermometer ) in which some physical change occurs with temperature, plus some means of converting this physical change into a numerical value ( e. g. the scale on a mercury thermometer ).

The word thermometer ( in its French form ) first appeared in 1624 in La Récréation Mathématique by J. Leurechon, who describes one with a scale of 8 degrees.

In about 1654 Ferdinando II de ' Medici, Grand Duke of Tuscany, made sealed tubes part filled with alcohol, with a bulb and stem, the first modern-style thermometer, depending on the expansion of a liquid, and independent of air pressure.

Many other scientists experimented with various liquids and designs of thermometer.

For example, when one observes a measured increase in temperature with a thermometer, that observation is based on assumptions about the nature of temperature and its measurement, as well as assumptions about how the thermometer functions.

The temperature change in the water is then accurately measured with a thermometer.

An example is a coffee-cup calorimeter, which is constructed from two nested Styrofoam cups and a lid with two holes, allowing insertion of a thermometer and a stirring rod.

They conducted their experiment with the bulb of a mercury thermometer as their object and with a bellows used to " quicken " the evaporation ; they lowered the temperature of the thermometer bulb down to, while the ambient temperature was.

* 1624 — The word thermometer ( in its French form ) first appeared in La Récréation Mathématique by J. Leurechon, who describes one with a scale of 8 degrees.

* 1654 — Ferdinando II de ' Medici, Grand Duke of Tuscany, made sealed tubes part filled with alcohol, with a bulb and stem, the first modern-style thermometer, depending on the expansion of a liquid, and independent of air pressure

In 1982 Seiko produced a watch with a small television screen built in, and Casio produced a digital watch with a thermometer as well as another that could translate 1, 500 Japanese words into English.

The value indicated by a simple wet-bulb thermometer often provides an adequate approximation of the thermodynamic wet-bulb temperature.

For example, a digital thermometer produces a numerical value that indicates the current state of a specific operational parameter.