thermometer

thermometric /therr'meuh me"trik/, thermometrical, adj.thermometrically, adv.
/theuhr mom"i teuhr/, n.
an instrument for measuring temperature, often a sealed glass tube that contains a column of liquid, as mercury, that expands and contracts, or rises and falls, with temperature changes, the temperature being read where the top of the column coincides with a calibrated scale marked on the tube or its frame.
[1615-25; THERMO- + -METER]

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▪ measurement instrument
 instrument for measuring the temperature of a system. Temperature measurement is important to a wide range of activities, including manufacturing, scientific research, and medical practice.

      The accurate measurement of temperature developed relatively recently in human history. The invention of the thermometer is generally credited to the Italian mathematician-physicist Galileo Galilei (Galileo) (1564–1642). In his instrument, built about 1592, the changing temperature of an inverted glass vessel produced an expansion or contraction of the air within it, which in turn changed the level of the liquid with which the vessel's long, openmouthed neck was partially filled. This general principle was perfected in succeeding years by experimenting with liquids such as mercury and by providing a scale to measure the expansion and contraction brought about in such liquids by rising and falling temperatures.

      By the early 18th century as many as 35 different temperature scales had been devised. The German physicist Daniel Gabriel Fahrenheit (Fahrenheit, Daniel Gabriel) in 1700–30 produced accurate mercury thermometers calibrated to a standard scale that ranged from 32°, the melting point of ice, to 96° for body temperature. The unit of temperature (degree) on the Fahrenheit temperature scale is 1/180 of the difference between the boiling (212°) and freezing points of water. The first centigrade scale (made up of 100 degrees) is attributed to the Swedish astronomer Anders Celsius (Celsius, Anders), who developed it in 1742. Celsius used 0° for the boiling point of water and 100° for the melting point of snow. This was later inverted to put 0° on the cold end and 100° on the hot end, and in that form it gained widespread use. It was known simply as the centigrade scale until in 1948 the name was changed to the Celsius temperature scale. In 1848 the British physicist William Thomson (later Lord Kelvin (Kelvin, William Thomson, Baron)) proposed a system that used the degree Celsius but was keyed to absolute zero (−273.15 °C); the unit of this scale is now known as the kelvin. The Rankine scale (see William Rankine (Rankine, William John Macquorn)) employs the Fahrenheit degree keyed to absolute zero (−459.67 °F).

      Any substance that somehow changes with alterations in its temperature can be used as the basic component in a thermometer. Gas thermometers work best at very low temperatures. Liquid thermometers are the most common type in use. They are simple, inexpensive, long-lasting, and able to measure a wide temperature span. The liquid is almost always mercury, sealed in a glass tube with nitrogen gas making up the rest of the volume of the tube.

      Electrical-resistance thermometers characteristically use platinum and operate on the principle that electrical resistance varies with changes in temperature. Thermocouples (thermocouple) are among the most widely used industrial thermometers. They are composed of two wires made of different materials joined together at one end and connected to a voltage-measuring device at the other. A temperature difference between the two ends creates a voltage that can be measured and translated into a measure of the temperature of the junction end. The bimetallic strip constitutes one of the most trouble-free and durable thermometers. It is simply two strips of different metals bonded together and held at one end. When heated, the two strips expand at different rates, resulting in a bending effect that is used to measure the temperature change.

      Other thermometers operate by sensing sound waves or magnetic conditions associated with temperature changes. Magnetic thermometers increase in efficiency as temperature decreases, which makes them extremely useful in measuring very low temperatures with precision. Temperatures can also be mapped, using a technique called thermography that provides a graphic or visual representation of the temperature conditions on the surface of an object or land area.

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Universalium. 2010.

Look at other dictionaries:

  • Thermometer — Thermometer …   Deutsch Wörterbuch

  • Thermometer [2] — Thermometer sind Vorrichtungen, die zur Bestimmung der Temperatur dienen. Es sollen einige Bemerkungen darüber beigebracht werden, wie man sich von der Richtigkeit der Angaben eines Thermometers überzeugen oder wie man ein solches prüfen kann.… …   Lexikon der gesamten Technik

  • Thermometer — Ther*mom e*ter (th[ e]r*m[o^]m [ e]*t[ e]r), n. [Thermo + meter: cf. F. thermom[ e]tre. See {Thermal}.] (Physics) An instrument for measuring temperature, founded on the principle that changes of temperature in bodies are accompanied by… …   The Collaborative International Dictionary of English

  • Thermometer [1] — Thermometer, Instrument zur Bestimmung von Temperaturen, im gewöhnlichen Sinne das Glasthermometer, eine an einem Ende verschlossene, am andern Ende zu einer Kugel erweiterte gläserne, luftleere kapillare Röhre, die nebst der Kugel zum Teil mit… …   Lexikon der gesamten Technik

  • Thermometer — (griech., Wärmemesser; hierzu Tafel »Thermometer« mit Text), Instrument zur Bestimmung des Wärmezustandes oder der Temperatur eines Körpers. Das T. ist wahrscheinlich von Galilei kurz vor 1600 erfunden und Thermoskop genannt worden; Santorio ist… …   Meyers Großes Konversations-Lexikon

  • Thermometer — Sn std. (18. Jh.) Neoklassische Bildung. Neubildung zu gr. thermós warm und gr. métron Maß . Das Fieberthermometer seit 1866 (entwickelt von dem englischen Arzt Clifford Albut).    Ebenso nndl. thermometer, ne. thermoneter, nfrz. thermomètre,… …   Etymologisches Wörterbuch der deutschen sprache

  • thermometer — (n.) 1630s, from Fr. thermomètre (1620s), coined by Jesuit Father Leuréchon from Gk. thermos hot (see THERMAL (Cf. thermal)) + metron measure (see METER (Cf. meter)). An earlier, Latinate form was thermoscopium (1610s). The earliest such device… …   Etymology dictionary

  • Thermometer — (v. gr.), Instrument zur Bestimmung der Temperatur der Körper, unabhängig von der unsicheren Angabe des Gefühles. Die Leistung des Th s beruht auf der Eigenschaft der Körper, sich bei zunehmender Wärme auszudehnen, bei abnehmender… …   Pierer's Universal-Lexikon

  • Thermometer — Thermomēter (grch.), Wärmemesser, physik. Instrument zur Bestimmung des Temperaturgrades; besteht gewöhnlich aus einer Glasröhre mit unten angeblasener Kugel, welche nebst einem Teil der Röhre mit Quecksilber oder Weingeist gefüllt ist, während… …   Kleines Konversations-Lexikon

  • Thermometer — Thermometer, oder Wärmemesser, besteht gewöhnlich aus einer Glaskugel mit einer engen Röhre, in welche Weingeist oder Quecksilber so eingeschlossen ist, daß diese Materie bei zunehmender Wärme in der Röhre steigt und bei zunehmender Kälte fällt.… …   Damen Conversations Lexikon

  • Thermometer — Thermometer, griech., Wärmemesser, Instrument zum Messen der Temperatur eines Körpers bei nicht zu hohen Temperaturgraden; vgl. Pyrometer. Die Einrichtung des T.s beruht auf der Ausdehnung der Körper durch die Wärme. Die dazu geeignetsten Körper… …   Herders Conversations-Lexikon

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