Rise in body temperature is one of the primary symptoms of illness was known to mankind as early as 400 B.C. The human hand was only used to assess a rise in temperature, but the extent or degree could not be measured. Can you imagine that human beings had to do without any temperature-measuring instrument until the 16^th and 17^th centuries?

Thermometer Facts

Yes, it was only in the 1500s that the first instrument to measure body temperature was invented. Although not a thermometer, what came into being was a thermoscope, and Galileo Galilei was working on it. In simple words, a thermoscope is a device that records a temperature change but does not assign any numerical value to the change. It was only in 1612 that Santorio Santorio attached a measuring scale to the thermoscope. Therefore, although Galileo is considered the inventor of the clinical thermometer, the lofty task of calibration was accomplished by the Italian scientist.

Galileo thermometer

How did mercury come to the scenario?

The original thermometer used water inside the tubes to contain the rise and fall in temperature. However, when this was carried to higher altitudes, the atmospheric pressure affected the level of the liquid. Thus, arose the need to replace water as the liquid inside these devices. It was Galileo again towards the early years of the 17^th century, who discovered that the use of an aqueous solution of high density could overcome this high-altitude issue! Water was replaced with alcohol (Galileo used wine) – which remained unaffected by barometric pressure.

The advent of the modern clinical thermometer

What is known to us today as the clinical thermometer was not invented until 1714. Daniel Fahrenheit was the inventor of the modern thermometer and here are the reasons why he chose mercury over other liquids –

• Having a high coefficient of expansion, mercury arrests even the slightest temperature change.
• Mercury is the only metal (metals are very good conductors of heat) that remains liquid at room temperature.
• It doesn’t stick to the glass tube!
• Its shiny appearance makes the changes clearly visible to the naked eye.

Infrared Thermoemeter

What if the mercury leaks or the glass tube breaks? That is where the clinical thermometers scored low. Many countries marked mercury thermometers as ‘risky’, especially, if you have a toddler at home! The period post-1990s, therefore, saw the emergence of digital thermometers or infrared thermometers. Today, digital thermometers come in various types. We will adhere to brevity while discussing the varieties here…

The factors upon which the differences in digital thermometers lie are –

Displays options – By display options we mean to say, whether your device displays temperatures in the Fahrenheit scale, Centigrade scale, or both the scales. Also, the maximum and minimum temperatures recorded are to be considered.

User interface – This count for the interface being used - analog or digital. Interfaces can also be categorized into serial or parallel.

Options for output – This mostly refers to a signal or an alarm for the user when the reading is done, or the accurate temperature value has been reached.

So, what makes digital thermometers stand alone? Remember the days when you had to place the thermometer underneath your tongue or armpit and wait for the mercury to rise to the accurate level? That's yet another point where the traditional thermometers score low – the digital counterparts are much faster with a high accuracy rate as well.

[For more articles, you can click on: Candy facts]

Meat Thermometer

Do you know what's special about a meat thermometer? It's basically a pricking instrument that comes attached with a measuring device. The long needle-like pricking portion is inserted in the meat or any other food that is semi-solid like fish! The needle needs to enter well inside the food to measure the core temperature. This is needed mostly while barbecuing meat especially.

Apart from being faster, portability, ease of use, large digital display of temperatures and the fact that you get them for a reasonable price makes the infrared thermometer preferred over the traditional clinical one!