Most people are familiar with the standard mercury thermometer and the relatively newer digital thermometers used by doctors and nurses. But there are actually several different types of thermometers for use in different environments and for different purposes. As instruments to measure temperature, they have a wide range of applications, including medical, scientific and engineering.

Here are some of the different types of thermometers in use today and their advantages:

• Mercury/alcohol thermometer: The traditional thermometer makes use of mercury or colored alcohol hermetically sealed inside a glass tube. When inserted under the tongue, in the armpit or inside the rectum, the heat from the body causes the mercury or alcohol to expand and rise up the graduated tube.  The advantages of these types of thermometers is that they are cheap, easy to read, can be submerged in liquids, require very little maintenance and are reliable. The disadvantages are that they break easily and there is risk of mercury poisoning if the glass tube breaks.

• Digital thermometer: A digital thermometer uses electronic heat sensors and displays the reading digitally on a small LCD screen located on one side of its broader end. Just like the mercury/alcohol thermometer, it is inserted under the tongue or in the armpit or inside the rectum to measure body temperature. The advantages of digital thermometers are that they are inexpensive, easy to read, require very little maintenance and give an accurate reading. The disadvantage is that they get damaged easily if dropped and the battery powering them eventually runs out.

• Tympanic thermometer: This is a type of digital thermometer that is used to measure body temperature by inserting it into the ear. Also called an ear thermometer, it is often used on patients who are in intensive care units (ICU) or who are under the influence of anesthetics during surgery. Its advantage is that it can obtain the temperature of a critically ill or unconscious patient within two seconds without causing pain.

• Temporal Artery thermometer:  Also called forehead tape thermometer, it is a use-and-throw  out digital thermometer for single use. The tape thermometer has a mild adhesive on one side that allows it to be taped to the forehead. It is a handy thermometer that can be taken anywhere. However, its use has been mostly discontinued because of inaccurate readings and also because of the difficulty to keep it stuck to the forehead.

• Infrared thermometer: This type of thermometer uses infrared technology to measure body temperature accurately and quickly.  It is also used in many other settings such as food preparation, air conditioning and automobiles. Its advantage is that the temperature of a patient can be obtained within just one second.

The above types of thermometers are some of the most widely used in medical application. The traditional mercury or alcohol thermometer is still the most popular as it is cheap, easy to use and gives accurate readings. But because of safety issues, the government has been recommending digital thermometers for use both at home and by medical professionals.