How Thermometers work: Temperature Scales


Thermometers are instrumental in the cooking process. A thermometer is a great way to know if your food is fully cooked, safe and ready to eat! Thermometers contain one very important aspect – a temperature scale. This is the fourth part of the “How Thermometers Work” series. We will breakdown the different temperature scales!

Researchers have gone to their graves trying to put together how exactly Mr. Fahrenheit invented his temperature scale.  There are several different stories about how the German physicist invented the scale. All of the stories seem to be very vague, as it is basically a guessing game when it comes to how, and why Daniel Fahrenheit invented the scale.  When it comes to the temperature scale, the freezing point is 32° and the boiling point is 212°.  Why did Daniel choose these numbers… to make math tests more difficult?  Were they just random? Both of those assumptions are wrong although between you and me, they did make math tests a little bit more difficult.  Some of the stories are compelling and others are just plain conspiracies, but there is one story that is believed to be correct.  Fahrenheit simply adopted Romer’s scale, and multiplied each value by four to eliminate the fractions and increase the granularity of the scale.  After this, he calibrated his scale between melting point of water and normal human body temperature. The melting point of ice was adjusted to 32°, so the 64 intervals would separate the two allowing him to mark degree lines on his instruments.


The Celsius scale is a little bit easier to explain than the Fahrenheit scale.  Celsius is a measurement between 0° (freezing point of water) and 100° (boiling point of water). It was Anders Celsius, a Swedish astronomer who developed the scale in 1742.  Along with developing the Celsius scale, he was also the first astronomer to measure the earth’s magnetic field.  Anders Celsius performed multiple experiments to develop his scale. According to his paper “Observations of two persistent degrees on a thermometer” his experiments consisted of latitude and atmospheric pressure finding that latitude and atmospheric pressure do have effect on the boiling point of water.

Pretty interesting isn’t it? Well folks we have come to the end of our “How Thermometers Work” series. Take a look back and check out series; Part 1: The Mercury Thermometer, Part 2: Dial Thermometers and Part 3:  Digital Thermometers.  Til next time!

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