A person’s temperature is measured using a thermometer. Thermometers may be a glass tube filled with mercury (silver colour) or alcohol (dyed red), a heat sensitive electronic probe, or an infrared measuring device which is gently placed in the ear canal to instantly measure the body’s temperature.
The most common method of measuring the body temperature is to place the thermometer bulb under the tongue, and leave it there for at least two minutes. The thermometer may also be placed in the anus, and this is very useful in children who might bite a glass thermometer. The third method is to place the instrument in the armpit, but this gives a reading about half a degree centigrade lower than the correct one.
The heat sensitive strips that can be placed on the forehead, give only a very rough guide to the patient’s true internal temperature.