A clinical thermometer has a constriction near the bulb in it. Due to this, mercury thread does not fall on removing the bulb from the mouth of the patient. It has a bulb of very thin glass attached with a capillary of a very fine bore. The bulb is long and thin instead of spherical. This helps the mercury in the bulb to acquire the patient's temperature more quickly and precisely. In Fahrenheit, the thermometer has the markings from 940 f to 1080 F. The normal temperature of a healthy person is 98.60 F, which is indicated by a red arrow on the scale. In Celsius degree, thermometers have markings from 350 C to 42 0 C. The normal temperature of a healthy person in degree Celsius is 370 C.

Laboratory thermometer consists of a bulb with a long capillary tube. The wall of the bulb is made thinner and the capillary tube is made narrower to make the thermometer more sensitive. Mercury thermometer expands and contracts according to the rise or fall in temperature. Laboratory thermometer can be used to measure both hot and cold substances. Usually, laboratory thermometer is made in Celsius scale which has scaled from -100 C to 1100 C.

Thermometer which is used to measure the maximum and minimum temperaature of a particular place within 24 hrs is called maximum and minimum thermometer. This kind of thermometer has both alcohol and mercury.

The thermometer which is used to measure the human body temperature and as mercury as thermometric substance is called clinical thermometer.

The thermometer which is used in laboratory to measure the temperature of substances between the temperature -37oC. to 357oC.

The thermometer which is used to measure the temperature of a human body and has mercury as the thermometric substance is called clinical thermometer.