How does Digital Thermometer Work?

Digital Thermometers are slowly replacing the conventional mercury thermometer due to the ease of taking reading. People often have the misconception that it contains mercury. Digital Thermometers are mercury free. These thermometers contain thermistor inside the tip which is used to measure the temperature. They provide quick and highly accurate results over the body temperature range. 

These thermometers are easy to read with LCD display on them. They are equipped with beep alarm & memory function and can record a wide range of temperature. Doctor’s thermometer which are mostly used can read temperature between 94oF and 105oF (35oC and 42oC). It is three in one thermometer as it can record oral, auxiliary and rectal temperatures.

The tip is said as the heart of the thermometer. It is the placed closed to the body part to measure the temperature of the body. The tip of the Thermometer contains thermistor to measure temperature. It is a ceramic semiconductor which is bonded in the tip with temperature sensitive epoxy. It is covered with a cap so to prevent it from the outer world. The cap may be made up of metal or stainless steel. Thermistor is responsible for converting the physical temperature into electrical signals.

Thermistor is a special kind of semiconductor in which the value of resistance changes with the change in temperature. Due to change in resistance value, the output voltage changes and the temperature change is detected.