Evolution of Medical Technology – The Thermometer

A fascinating part of the medical device industry is the constant changes in technology. Improvements made to medical devices today render yesterday’s innovations obsolete. In honor of flu season, we will take a look at the history of the thermometer. From its original form using liquids that expand and contract inside a glass column to its current state, the thermometer has come a long way. Below is a brief timeline of events that have led us to today’s thermometer.

The Evolution Of The Thermometer

The Thermoscope

The thermometer dates back to the early 1600s, with Galileo’s invention of the “thermoscope.” Galileo’s device could determine whether temperature was rising or falling, but was not able to detect the actual scale of the temperature. In 1612, Italian inventor and physician Sanctorius was the first to put a numerical scale on the thermoscope. His product was also designed for taking temperature from a patient’s mouth. However, neither Galileo’s nor Sanctorius’ thermoscopes were very accurate.

Standardized Scales

In 1709, Daniel Gabriel Fahrenheit invented his first thermometer using alcohol. He later introduced the mercury thermometer in 1714, which was more accurate and predictable. The Fahrenheit temperature scale was standardized in 1724 with a freezing point of 32 degrees and a boiling point of 212 degrees. Fahrenheit’s mercury thermometer is recognized as the first modern thermometer with a standardized scale.

The Celsius scale was invented in 1742 by Anders Celsius, with a freezing point of 0 degrees and a boiling point of 100 degrees. This scale was accepted into the international conference on weights and measurements in 1948. The Kelvin Scale, measuring extreme temperatures, was developed by Lord Kelvin in 1848.

Registering Thermometers

Early versions of the thermometer were not able to hold the temperature after they were moved. You can imagine how this made it hard for doctors to correctly read a patient’s temperature. The first thermometer that could register and hold onto temperature was built by James Six in 1782. Today, it is known as Six’s thermometer. Since then, the mercury thermometer was adapted to read a patients temperature after leaving the body. Registering thermometers are still used today and are reset by shaking down the mercury to the bottom of the tube.

The Modern Devices

Modern Day Thermometers

This brings us to the first practical clinical thermometer, which was invented in 1867 by Sir Thomas Allbutt. The device was portable, about 6 inches long and was capable of recording a patient’s temperature in 5 minutes. Now, there are a few options for clinical and home use. Liquid filled thermometers have been adapted based on the designs of inventors like Fahrenheight and Six are still used today. Digital thermometers, like the Omron Compact Digital Thermometer, are capable of finding a temperature and producing an electronic number within a minute of use. Digital ear thermometers also produce a quick and accurate temperature. Dr. Jacob Fraden invented an infared thermometer called the Thermoscan Human Ear Thermometer in 1984. These thermometers use an infared light to scan the heat radiation in a patient’s ear or forehead.

The thermometer, like many medical devices, has made strides in efficiency and accuracy. As medical technology continues to advance, businesses in the medical device industry must be prepared to move with it.

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