The evolution of the thermometer

27 September, 2015

Thermometers have been a crucial invention, which has helped us in a variety of areas in science. Engineering, meteorology, and biology are just a few sectors where the thermometer can be crucial to success or failure.

The melting point of materials helps with soldering and tempering in metal work. The temperature on a summers day can inform us of what we should wear. A significant change in body temperature can be the first real warning sign something is wrong with your health.

So how did this crucial tool come into being?

The creation of the thermometer

The creation of the thermometer was a process rather than an outright invention. The use of temperature as a way of detecting illness dates back to the time of Hippocrates in 370 BC when they used their hand to detect cold or heat.

The first crude temperature measure was created by an Italian inventor called Galileo Galilei. His invention could show if it was getting hotter or colder but did not have a scale. The invention is now known as a thermoscope and led on to the creation thermometer.

From here a variety of scientists took this crude form of the thermometer and tried to improve it. This included Santorio (1561–1636), inventing the first oral thermometer and Christiaan Huygens, who added a scale that measured from the freezing point to the boiling point of water.

How the modern day thermometer came to be

However, it was Gabriel Daniel Fahrenheit who first used mercury in a thermometer. He found mercury performed better in a thermometer as it expands and contracts a lot faster than other liquids.

He was also the creator of the ‘Fahrenheit scale’, funnily enough, named after himself. His scale was based on the human body temperature, which was 100oF (this has been reduced now to 98.6oF).

In 1742, Anders Celsius reintroduced the centigrade scale, sometimes referred to as ‘Celsius’ for obvious reasons, but this was not widely used until the 19thcentury.

These two scales and the introduction of mercury as the liquid of choice for measuring temperature set the foundations for the modern-day thermometer. However, they were made a lot smaller over the coming decades.

First clinical use of thermometers

Carl Wunderlich is the person accredited to discovering the ‘normal temperature’ of the human body, which is 37oC (98.6oF). However, it was he who told the clinical world that there isn’t one normal temperature for the human body, but a range from a lower limit to an upper limit of 38oC (100.4oC). Anything over this temperature was seen to be a fever and an indication of an illness or disease.

With Wunderlich’s discoveries, it made clinical thermometers paramount in diagnosing patients. The only stumbling block was the size of them, as they were almost a foot long and took 20 minutes to get an accurate temperature.

Up stepped Thomas Clifford Allbutt, who in 1866 managed to create a thermometer that was only 6 inches in length and could take a temperature accurately in just 5 minutes. This discovery made thermometers a lot more user-friendly and the rest, they say, is history.

The thermometer, since then, has been brought into the 21st century. You can now get products such as electronic, electronic direct and predictive, infra-red ear thermometers, and dot-matrix or phase-change thermometers.

Thermometers at Ashtons

As thermometers have become an inescapable necessity, we have tried to source a wide variety so we can cater for every need.

You can view our range of thermometers on our online ordering website. If you can find what you are looking for, please don’t hesitate to call our Customer Services Team on 0345 222 3550, and they will do their utmost to source what you require.