HOW DO EAR THERMOMETERS WORK?

Kevin Kennedy

These devices are also called tympanic thermometers. This is because they take measurements from the tympanic membrane – the ‘drum skin’ of your eardrum. Unlike traditional mercury thermometers, which use the expansion of mercury at higher temperatures to measure those in the body, tympanic thermometers measure infrared radiation. Infrared radiation is a form of electromagnetic radiation, like light or radio waves, that is given off by anything that has a temperature.

The probe part of the thermometer is inserted into the ear, where its infrared radiation sensor is within range of the membrane and can get a reading. For hygiene, the probe has a disposable plastic cover which the infrared radiation can pass through, and an extension can be used to place it in the ear of unconscious surgery patients. The reading is much quicker and convenient – just two seconds compared to two minutes for an accurate rectal thermometer reading.