Thermometer

From ArticleWorld

A thermometer is a device used for measuring temperature. It especially refers to a thin, graduated glass tube with a small bulb at the bottom which contains a so-called thermometric liquid like mercury or alcohol. The mercury (or alcohol) expands into the tube upon an increase in temperature, hence allowing the user to take the correct reading from the tube.

Types

Mercury thermometers, though old-fashioned, are accurate for most purposes and very inexpensive. Digital thermometers display the readings electronically but are more expensive. Thermometers are used mainly for both medical and meteorological purposes.

Medical thermometers

The following are different types of thermometers used for measuring the human body temperature:

• Oral thermometers:

These consist of a long slender bulb which is inserted in the mouth. It is best for adults and small children. The thermometer is shaken vigorously before use so that the mercury falls down the tube and into the bulb to avoid an inaccurate reading. It is then inserted in the mouth and placed under the tongue for a few minutes.

• Electronic ear thermometers:

These thermometers, which are inserted in the ear, are especially useful for an invalid or someone who is seriously ill.

• Rectal thermometers:

Rectal thermometers are most accurate for children below the age of five. Usually, a lubricant (such as petroleum jelly) is used to lubricate the bulb end before the thermometer is inserted into the rectum. The rectal reading will be higher than an oral reading by about 0.5° C.