What is the difference between the lab thermometer and teh clinical thermometer?

Answer 1

1. lab thermometer
A Galileo thermometer, Galilean thermometer or thermoscope is a thermometer made of a sealed glass cylinder containing a clear liquid. Suspended in the liquid are a number of weights. Commonly those weights are themselves sealed glass containers with coloured liquid for an attractive effect. As the liquid changes temperature it changes density and the suspended weights rise and fall to stay at the position where their density is equal to that of the surrounding liquid. If the weights differ by a very small amount and are ordered such that the least dense is at the top and most dense at the bottom, they can form a temperature scale.

The temperature is typically read from an engraved metal disc on each weight. The lowest weight of the top set of weights indicates the ambient temperature. To achieve this requires manufacturing the weights to a tolerance of less than 1/1000 of a gram.


2. Medical clinical thermometers are traditionally mercury-in-glass thermometers used for measuring human body temperature, with the tip of the thermometer being inserted either into the mouth (oral temperature), under the armpit (axilliary temperature) or into the rectum via the anus (rectal temperature).

The traditional mercury filled medical thermometer works in the same way as a meteorological maximum thermometer. The thermometer consists of containing mercury attached to a small tube. As the temperature rises, the mercury expands and flows up the tube. The temperature is obtained by reading the scale inscribed on the side of the thermometer. There is a constriction in the neck close to the bulb. As the temperature rises the mercury is forced up through the constriction by the force of the expansion. When the temperature falls the column of mercury breaks at the constriction and cannot return to the bulb thus remaining stationary in the tube. To reset the thermometer it must be swung sharply.


Close up of a maximum thermometer. The break in the column of mercury is visible.Oral temperature may only be taken from a patient who is capable of holding the thermometer in their mouth correctly and securely, which generally excludes small children or people who are overcome by coughing or vomiting (this is now less of a problem with fast-reacting digital thermometers, but was certainly an issue with mercury thermometers, which took several minutes to register a temperature). Another counter-indication is if the patient has drunk a hot or cold liquid beforehand, in which case one has to wait or use another method.

Rectal temperature, especially if taken by a person other than the patient, should be facilitated with the use of lubricant (such as petroleum jelly (now discouraged) or a water-based personal lubricant). Although rectal temperature is the most accurate, this method may be considered embarrassing in some countries or cultures, especially if used on patients older than young children. Rectal temperature is considered the method of choice for infants for the general public; however, "the rectal route is least desirable in infants" from a nursing point of view. (Fundamentals of Nursing by Barbara Kozier et al, 7th edition, p. 495)


Electronic clinical thermometerIn the 1990s, mercury thermometers were found too risky to handle and have largely been replaced with electronic thermometers, or, more rarely, thermometers based on liquids other than mercury. In some places it may be illegal to sell products which can contain mercury, such as thermometers. Both kinds may be used orally, axilliarily, or rectally.

Other kinds of medical thermometers exist such as the tympanic thermometer that measures the temperature of the tympanum by infrared measurement, and the band thermometer that are applied to the patient's brow.