A clinical mercury thermometer

The thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A mercury-in-glass thermometer, invented by German physicist Daniel Gabriel Fahrenheit, is a Thermometer consisting of mercury in a Glass Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature In atmospheric sciences ( Meteorology, Climatology and related fields the temperature gradient (typically of air, more generally of any Fluid The word thermometer is derived from two smaller word fragments: thermo from the Greek for heat and meter also from Greek, meaning to measure. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature A thermometer has two important elements: the temperature sensor (e. g. the bulb on a mercury thermometer) in which some physical change occurs with temperature, plus some means of converting this physical change into a value (e. Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum g. the scale on a mercury thermometer). Industrial thermometers commonly use electronic means to provide a digital display or input to a computer.

Thermometers can be divided into two groups according to the level of knowledge about the physical basis of the underlying thermodynamic laws and quantities. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " For primary thermometers the measured property of matter is known so well that temperature can be calculated without any unknown quantities. Examples of these are thermometers based on the equation of state of a gas, on the velocity of sound in a gas, on the thermal noise (see Johnson–Nyquist noise) voltage or current of an electrical resistor, and on the angular anisotropy of gamma ray emission of certain radioactive nuclei in a magnetic field. In Physics, velocity is defined as the rate of change of Position. Johnson–Nyquist noise ( thermal noise, Johnson noise, or Nyquist noise) is the electronic noise generated by the thermal agitation Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. Anisotropy (pronounced with stress on the third syllable ˌænaɪˈsɒtrəpi is the property of being directionally dependent as opposed to Isotropy, which means homogeneity Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges

Secondary thermometers are most widely used because of their convenience. Also, they are often much more sensitive than primary ones. For secondary thermometers knowledge of the measured property is not sufficient to allow direct calculation of temperature. They have to be calibrated against a primary thermometer at least at one temperature or at a number of fixed temperatures. Such fixed points, for example, triple points and superconducting transitions, occur reproducibly at the same temperature. In Thermodynamics, the triple point of a substance is the Temperature and Pressure at which three phases (for example Gas, Liquid Superconductivity is a phenomenon occurring in certain Materials generally at very low Temperatures characterized by exactly zero electrical resistance

Internationally agreed temperature scales are based on fixed points and interpolating thermometers. The most recent official temperature scale is the International Temperature Scale of 1990. The International Temperature Scale of 1990 ( ITS-90) is an equipment calibration standard for making measurements on the Kelvin and It extends from 0. 65 K to approximately 1358 K (−272. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic 5 °C to 1085 °C). The Celsius Temperature scale was previously known as the centigrade scale.

Early history

Galileo thermometer

Various authors have credited the invention of the thermometer to Abū Alī ibn Sīnā (usually known as Avicenna), Cornelius Drebbel, Robert Fludd, Galileo Galilei or Santorio Santorio. A Galileo Thermometer, Galilean thermometer (named after Italian physicist Galileo Galilei) or thermoscope is a thermometer made TemplateInfobox Muslim scholars --> ( Persian /ابو علی الحسین ابن عبدالله ابن سینا (born Cornelius Jacobszoon Drebbel ( Alkmaar, Holland, 1572 - London, November 7 1633) was the Dutch Inventor Robert Fludd, also known as Robertus de Fluctibus (1574 Bearsted Kent &ndash September 8 1637, London) was a prominent Galileo Galilei (15 February 1564 &ndash 8 January 1642 was a Tuscan ( Italian) Physicist, Mathematician, Astronomer, and Philosopher Santorio Santorio ( March 29 1561 Koper &ndash February 22 1636 Venice) also called Santorio Santorii, But the thermometer was not a single invention, it was a development.

Philo and Hero of Alexandria knew of the principle that certain substances, notably air, expand and contract and described a demonstration, in which a closed tube partially filled with air had its end in a container of water. Philo (20 BC - 50 AD) known also as Philo of Alexandria (gr Φίλων ὁ Ἀλεξανδρεύς Philo Judaeus, Philo Judaeus of Alexandria Hero (or Heron) of Alexandria ( Ήρων ο Αλεξανδρεύς) (c ^[1] The expansion and contraction of the air caused the position of the water/air interface to move along the tube.

Similar devices used to show the hotness and coldness of the air with a tube in which the water level is controlled by the expansion and contraction of the air, were developed by Avicenna in the early 11th century,^[2][3] and by several European scientists in the 16th and 17th centuries, notably Galileo Galilei. Galileo Galilei (15 February 1564 &ndash 8 January 1642 was a Tuscan ( Italian) Physicist, Mathematician, Astronomer, and Philosopher As a result, devices were shown to produce this effect reliably, and the term thermoscope was adopted because it reflected the changes in sensible heat (the concept of temperature was yet to arise). A Galileo Thermometer, Galilean thermometer (named after Italian physicist Galileo Galilei) or thermoscope is a thermometer made Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature The difference between a thermoscope and a thermometer is that the latter has a scale^[4]. Though Galileo is often said to be the inventor of the thermometer, what he produced was a thermoscope.

Galileo also discovered that objects (glass spheres filled with aqueous alcohol) of slightly different densities would rise and fall, which is nowadays the principle of the Galileo thermometer (shown). Galileo Galilei (15 February 1564 &ndash 8 January 1642 was a Tuscan ( Italian) Physicist, Mathematician, Astronomer, and Philosopher A Galileo Thermometer, Galilean thermometer (named after Italian physicist Galileo Galilei) or thermoscope is a thermometer made Today such thermometers are calibrated to a temperature scale.

The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani: the first showing a scale and thus constituting a thermometer was by Robert Fludd in 1638. Giuseppe Biancani (in Latin, Josephus Blancanus) (1566-1624 was an Italian Jesuit astronomer mathematician and selenographer, after Robert Fludd, also known as Robertus de Fluctibus (1574 Bearsted Kent &ndash September 8 1637, London) was a prominent This was a vertical tube, with a bulb at the top and the end immersed in water. The water level in the tube is controlled by the expansion and contraction of the air, so it is what we would now call an air thermometer. ^[5]

The first person to put a scale on a thermoscope is variously said to be Francesco Sagredo^[6] or Santorio Santorio^[7] in about 1611 to 1613. Santorio Santorio ( March 29 1561 Koper &ndash February 22 1636 Venice) also called Santorio Santorii,

The word thermometer (in its French form) first appeared in 1624 in La Récréation Mathématique by J. Leurechon, who describes one with a scale of 8 degrees^[8].

The above instruments suffered from the disadvantage that they were also barometers, i. History The first barometer is thought to have been built unintentionally by Gasparo Berti, sometime between 1640 and 1643 e. sensitive to air pressure. In about 1654 Ferdinando II de' Medici, Grand Duke of Tuscany, made sealed tubes part filled with alcohol, with a bulb and stem, the first modern-style thermometer, depending on the expansion of a liquid, and independent of air pressure^[9]. Ferdinando II de' Medici Grand Duke of Tuscany ( 14 July 1610 &ndash 23 May 1670) ruled as Grand Duke of Tuscany from 1621 to 1670 Many other scientists experimented with various liquids and designs of thermometer.

However, each inventor and each thermometer was unique—there was no standard scale. In 1665 Christian Huygens suggested using the melting and boiling points of water as standards, and in 1694 Carlo Renaldini proposed using them as fixed points on a universal scale. Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch In 1701 Isaac Newton proposed a scale of 12 degrees between the melting point of ice and body temperature. Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements Core temperature, also called core body temperature, is the operating Temperature of an Organism, specifically in deep structures of the body such as the Finally in 1724 Daniel Gabriel Fahrenheit produced a temperature scale which now (slightly adjusted) bears his name. Year 1724 ( MDCCXXIV) was a Leap year starting on Saturday (link will display the full calendar of the Gregorian calendar (or a He could do this because he manufactured thermometers, using mercury (which has a high coefficient of expansion) for the first time and the quality of his production could provide a finer scale and greater reproducibility, leading to its general adoption. Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum In 1742 Anders Celsius proposed a scale with zero at the boiling point and 100 degrees at the melting point of water^[10], though the scale which now bears his name has them the other way around. Year 1742 ( MDCCXLII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Anders Celsius ( November 27, 1701 &ndash April 25, 1744 in Uppsala) was a Swedish astronomer.

In 1866 Sir Thomas Clifford Allbutt invented a clinical thermometer that produced a body temperature reading in five minutes as opposed to twenty^[11]. Year 1866 ( MDCCCLXVI) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common Sir Thomas Clifford Allbutt ( July 20, 1836 – February 22, 1925) was a British Physician and inventor of the Clinical Medical thermometers are used for measuring human Body temperature, with the tip of the thermometer being inserted either into the mouth ( oral temperature

Types of thermometers

Mercury-in-glass thermometer

Cooking thermometers used to measure the temperature of steamed milk

Thermometers have been built which utilise a range of physical effects to measure temperature. A mercury-in-glass thermometer, invented by German physicist Daniel Gabriel Fahrenheit, is a Thermometer consisting of mercury in a Glass Most thermometers are originally calibrated to a constant-volume gas thermometer. A gas thermometer measures Temperature by the variation in volume or pressure of a gas Temperature sensors are used in a wide variety of scientific and engineering applications, especially measurement systems. Temperature systems are primarily either electrical or mechanical, occasionally inseparable from the system which they control (as in the case of a mercury thermometer). A mercury-in-glass thermometer, invented by German physicist Daniel Gabriel Fahrenheit, is a Thermometer consisting of mercury in a Glass

• Alcohol thermometer
• Beckmann differential thermometer
• Bi-metal mechanical thermometer
• Electrical resistance thermometer
• Galileo thermometer
• Infrared thermometer
• Liquid Crystal Thermometer
• Medical thermometer (e. A Beckmann thermometer is a device used to measure small differences of temperature but not absolute temperature values A bi-metallic strip is used to convert a temperature change into mechanical displacement Resistance thermometers, also called resistance temperature detectors ( RTD s are Temperature Sensors that exploit the predictable change in A Galileo Thermometer, Galilean thermometer (named after Italian physicist Galileo Galilei) or thermoscope is a thermometer made Infrared thermometers measure Temperature using Blackbody radiation (generally Infrared) emitted from objects A liquid crystal thermometer or plastic strip thermometer is a type of Thermometer that contains heat-sensitive ( thermochromic) Liquid crystals Medical thermometers are used for measuring human Body temperature, with the tip of the thermometer being inserted either into the mouth ( oral temperature g. oral thermometer, rectal thermometer, basal thermometer)
• Mercury-in-glass thermometer
• Reversing thermometer
• Silicon bandgap temperature sensor
• Six's thermometer- also known as a Maximum minimum thermometer
• Thermistor
• Thermocouple
• Coulomb blockade thermometer
• Pill Thermometer

Calibration

Thermometers can be calibrated either by comparing them with other certified thermometers or by checking them against known fixed points on the temperature scale. A mercury-in-glass thermometer, invented by German physicist Daniel Gabriel Fahrenheit, is a Thermometer consisting of mercury in a Glass Unlike most conventional mercury Thermometers, a reversing thermometer is able to record a given Temperature The silicon bandgap temperature sensor is an extremely common form of temperature sensor ( Thermometer) used in electronic equipment Six's thermometer is a Thermometer, also known as a Maximum minimum thermometer, which can measure the Maximum and Minimum Temperature A thermistor is a type of Resistor with resistance varying according to its Temperature. In Electrical engineering and industry thermocouples are a widely used type of temperature sensor and can also be used as a means to convert thermal Potential In physics a Coulomb blockade, named after Charles-Augustin de Coulomb, is the increased resistance at small bias voltages of an electronic device comprising A pill thermometer is an ingestible Thermometer in pill form that allows a person's Core temperature to be constantly monitored The best known of these fixed points are the melting and boiling points of pure water. (Note that the boiling point of water varies with pressure, so this must be controlled. )

The traditional method of putting a scale on a liquid-in glass or or liquid-in-metal thermometer was in three stages:

• 1. Immerse the sensing portion in a stirred mixture of pure ice and water and mark the point indicated when it had come to thermal equilibrium.
• 2. Immerse the sensing portion in a steam bath at one standard atmosphere (101. 325 kPa = 760 mm Hg) and again mark the point indicated.
• 3. Divide the distance between these marks into equal portions according to the temperature scale being used.

Other fixed points were used in the past are the body temperature (of a healthy adult male) which was originally used by Fahrenheit as his upper fixed point (96 degrees F to be a number divisible by 12) and the lowest temperature given by a mixture of salt and ice, which was originally the definition of 0 degrees Fahrenheit^[12]. Core temperature, also called core body temperature, is the operating Temperature of an Organism, specifically in deep structures of the body such as the Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 (This is an example of a Frigorific mixture). A frigorific mixture is a mixture of two or more chemicals that achieve an equilibrium temperature independent of the temperature that the two chemicals started at As body temperature varies, the Fahrenheit scale was later changed to use an upper fixed point of boiling water at 212 degrees^[13]. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724

These have now been replaced by the defining points in the International Temperature Scale of 1990, though in practice the melting point of water is more commonly used than its triple point, the latter being more difficult to manage and thus restricted to critical standard measurement. The International Temperature Scale of 1990 ( ITS-90) is an equipment calibration standard for making measurements on the Kelvin and Nowadays manufacturers will often use a thermostat bath or solid block where the temperature is held constant relative to a calibrated thermometer. A thermostat is a device for regulating the Temperature of a System so that the system's temperature is maintained near a desired setpoint Other thermometers to be calibrated are put into the same bath or block and allowed to come to equilibrium, then the scale marked, or any deviation from the instrument scale recorded^[14]. For many modern devices calibration will be stating some value to be used in processing an electronic signal to convert it to a temperature .

Specialist uses of thermometers

• Candy thermometer
• Meat thermometer
• Medical thermometer

See also

• Automated airport weather station
• Timeline of temperature and pressure measurement technology
• Comparison of temperature scales
• Resistance Thermometer
• Thermistors
• Thermocouples
• Thermogenerator
• Silicon bandgap temperature sensor

Notes

References

• History Channel - Invention - Notable Modern Inventions and Discoveries
• About - Thermometer - Thermometers - Early History, Anders Celsius, Gabriel Fahrenheit and Thomson Kelvin.
• Thermometers and Thermometric Liquids - Mercury and Alcohol.
• The NIST Industrial Thermometer Calibration Laboratory

Further reading

• Middleton, W. E. K. (1966). A history of the thermometer and its use in meteorology. Baltimore: Johns Hopkins Press. Reprinted ed. 2002, ISBN 0801871530.

External links

• History of Temperature and Thermometry
• The Chemical Educator, Vol. 5, No. 2 (2000) The Thermometer—From The Feeling To The Instrument