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7/365 – Thermometer


Thermometers measure temperature, by using materials that change in some way when they are heated or cooled. In a mercury or alcohol thermometer the liquid expands as it is heated and contracts when it is cooled, so the length of the liquid column is longer or shorter depending on the temperature. Modern thermometers are calibrated in standard temperature units such as Fahrenheit or Celsius and Kelvin.

Early History
In 1593, Galileo Galilei invented a rudimentary water thermoscope, which for the first time, allowed temperature variations to be measured. In 1612, the Italian inventor Santorio became the first inventor to put a numerical scale on his thermoscope. It was perhaps the first crude clinical thermometer, as it was designed to be place in a patient’s mouth for temperature taking. In 1654, the first enclosed liquid-in-a-glass thermometer was invented by the Grand Duke of Tuscany, Ferdinand II. The Duke used alcohol as his liquid.

Fahrenheit Scale – Daniel Gabriel Fahrenheit
Daniel Gabriel Fahrenheit was the German physicist who invented a alcohol thermometer in 1709, and the mercury thermometer in 1714. In 1724, he introduced the standard temperature scale that bears his name – Fahrenheit Scale.

Centigrade Scale – Anders Celsius
The Celsius temperature scale is also referred to as the “centigrade” scale. Centigrade means “consisting of or divided into 100 degrees”. In 1742, the Celsius scale was invented by Swedish Astronomer Anders Celsius.

Kelvin Scale – Lord Kelvin
Lord Kelvin took the whole process one step further with his invention of the Kelvin Scale in 1848. The Kelvin Scale measures the ultimate extremes of hot and cold. Kelvin developed the idea of absolute temperature, what is called the “Second Law of Thermodynamics”, and developed the dynamical theory of heat.

Mouth Thermometers
In 1612, the Italian inventor Santorio invented a mouth thermometer and perhaps the first crude clinical thermometer. However, it was both bulky, inaccurate, and took too long to get a reading. The first doctors Hermann Boerhaave, Gerard L.B. Van Swieten founder of the Viennese School of Medicine, and Anton De Haen. These doctors found temperature correlated to  the progress of an illness, however, few of their contemporaries agreed, and the thermometer was not widely used.

First Practical Medical Thermometer
Sir Thomas Allbutt (1836–1925) invented the first practical medical thermometer used for taking the temperature of a person in 1867. It was portable, 6 inches in length and able to record a patient’s temperature in 5  min.

Ear Thermometer
During World War II, Theodore Hannes Benzinger invented the ear thermometer. David Phillips invented the infra-red ear thermometer in 1984. Dr. Jacob Fraden, CEO of Advanced Monitors Corporation, invented the world’s best-selling ear thermometer, the Thermoscan® Human Ear Thermometer.

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