Thermometers are a compilation of work of many people throughout the years. Galileo Galilei (1564–1642) invented a rudimentary water thermometer in 1593 and temperature variations were measured for the first time. Italian inventor Santorio Santorio (1561–1636), who belonged to a group of Venetian scientists, was the first inventor to put a numerical scale on it. The accuracy of this thermometer wasn’t good since the variance in air pressure was not taken into consideration. In 1654 the Grand Duke of Tuscany, Ferdinand II (1610-1670) produced the first sealed liquid-in-glass thermometer.
In 1714, Gabriel Fahrenheit invented the first mercury thermometer called thermoscope. This thermometer was much more accurate. Swedish scientist Anders Celsius (1701-1744) came up with the idea of a thermometer scale in 1741 dividing the freezing and boiling points of water into 100 degrees. Jean Pierre Cristin (1683-1755) produced later on the Centigrade scale used today. In the 1800 Sir William Herschel came up with the idea of using infrared to measure temperature. David Phillips, almost two centuries later, invented the first infrared ear thermometer.
However, non-contact infrared thermometers are more reliable. They are now available in the market. It takes less than 500 mSec to take your body temperature with a non-contact thermometer.