Lektion 1 Sidan 2 av 5 © Pentronic AB 2017-01-19 ---------------------------------------------------------------------------------------------------------------------------------------------------- However, the thermometer had no real practical use until 1714, when the German physicist Daniel Gabriel Fahrenheit developed a temperature scale that made it possible to take comparative measurements. He is also considered to be the inventor of the mercury thermometer as it is today – that is, mercury inside a closed glass tube. It is worth pointing out that the glass thermometers containing mercury that may still be in use are being used by special exemption. Mercury is a stable substance but it becomes dangerous out in the environment. Today we use other liquids such as coloured alcohol. The temperature scales Fahrenheit Fahrenheit created a 100-degree scale in which zero degrees was the temperature of a mixture of sal ammoniac and snow – the coldest he could achieve in his laboratory in Danzig. As the upper fixed point he used the internal body temperature of a healthy human being and gave it the value of 100°F. In degrees Celsius this scale corresponds approximately to the range of -18 to +37 degrees. With this issue Pentronic begins its training in Becausetemperature it can be awkwardmeasurement to achieve .the We upper will fixed start point , he apparently introduced the more practical fixed points of +32°F and +96°F, which were respectively the freezing point of lesson 1 with a historical review and then continuewater and with the temperaturethermodynamics, of a human being’sheat armpittransfer. and quality assurance with calibration. Only after that will we move on to temperature sensors – primarily thermocouples and Pt100s.Fahrenheit’s scale was later extended to the boiling point of water, which was assigned the temperature value of +212°F. 212 °F, boiling point of water LESSON 1 THE NATURE AND HISTORY OF TEMPERATURE 100 °F, internal body temperature of a human 96 °F, temperature of a human armpit TEMPERATURE – HEAT also developed simple scales, which Temperature does not exist. It is a included the divisions of 40 and 80 32 °F, freezing point of water theoretical model constructed so that degrees between the “fixed points” humans can measure, compare and of the high summer temperature and 0 °F, snow/sal ammoniac mixture understand changes of kinetic energy the low winter temperature. among a body’s smallest compo­ However, the thermometer had no nents such as atoms and molecules. real practical use until 1714, when Fahrenheit’s mercury-in-glass thermo- In contrast, heat does exist and the German physicistFahrenheit Daniel Gabriel’s mercury -imetern-glas withs thermometer the reference with points the reference that points that were apparently is described as being the amount of Fahrenheit developedused a temperature. were apparently used. kinetic energy inside a body. From scale that made it possible to take this it follows that everything above comparative measurements.Anders HeCelsius is absolute zero (­273.15°C) is heat. also considered to beAt the the inventor same time, people Becausewere considering it can be having awkward a scale to with more natural divisions But this definition leads to peculiar of the mercury thermometerwhereby as 0 degreesit wasachieve defined the as upper the melting fixed pointpoint, of heice and 100 as the boiling point of effects. For example, an iceberg is today – that is, mercurywater. inside We know a that even apparently before 1737introduced Linneaus the wasmore using this scale, which was later contains more heat than a cup of closed glass tube. named after the Swedishpractical astronomer fixed Anderspoints Celsius.of +32°F and coffee, because the iceberg contains It is worth pointing out that the +96°F, which were respectively the a greater amount of energy. glass thermometers containing freezing point of water and the tem­ Anyone who puts a finger on the mercury that may still be in use are perature of a human being’s armpit. iceberg and the coffee respectively being used by special exemption. Fahrenheit’s scale was later ex­ experiences the opposite. What Mercury is a stable substance but tended to the boiling point of water, we then feel is the heat, the kinetic it becomes dangerous out in the which was assigned the temperature energy, at a given point. Temper­ environment. Today we use other value of +212°F. ature is our tool for describing this liquids such as coloured alcohol. experience in a comparable and ANDERS CELSIUS reproducible way. The coffee feels At the same time, people were hotter than the iceberg because it THE TEMPERATURE SCALES considering having a scale with more has a higher temperature. natural divisions whereby 0 degrees FAHRENHEIT was defined as the melting point of THE PIONEERS Fahrenheit created a 100­degree ice and 100 as the boiling point of The thermometer was invented at the scale in which zero degrees was water. We know that even before beginning of the 17th century by the the temperature of a mixture of sal 1737 Linneaus was using this scale, Italians Galileo and Santorio at the ammoniac and snow – the coldest which was later named after the Accademia del Cimento in Florence he could achieve in his laboratory in Swedish astronomer Anders Celsius. and by the Dutchman Drebbel. The Danzig. In 1742 Celsius launched the first thermometer consisted of a As the upper fixed point he used scale in reverse order, arguing that spiral­shaped glass tube filled with the internal body temperature of a water should boil at 0 degrees and alcohol. The tube was not closed healthy human being and gave it the freeze at 100. Not until eight years and therefore the instrument also value of 100°F. In degrees Celsius later was the scale reversed by his measured the air pressure at the this scale corresponds approximately successor as professor at Uppsala same time. The academy in Florence to the range of ­18 to +37 degrees. University, the mathematician Mårten A finger feels how the heat energy (also called thermal energy) moves (see the ar- Anders Celsius. row) in or out depending on whether the temperature of the object being touched is higher or lower than the finger’s. Strömer. As an interesting aside, it p V = R T where Temperature is a measurement is worth mentioningLektion 1 that asLektion early 1 as Sidan 3 av 5 Sidan 3 av 5 of what is regarded as the “anima­ p = the gas pressure © Pentronic AB © Pentronic1743, AB Professor Christin in Lyon had 2017-01-19 2017-01-19 tion” or movements of the smallest ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------V = the enclosed ---------------------- volume (in moles) In 1742 Celsius launchedIn 1742built the Celsius thescale firstlaunched in reverse mercury the order, scale arguing thermometerin reverse that order,water arguingshould boil thatR at water= 0 the should universal boil at 0gas constant components of matter such as atoms degrees and freezedegrees at with100. andNot the freezeuntil Celsius eight at 100. years scaleNot later until was“the eight the rightyears scale later reversedway was theby hisscaleT = reversedthe absolute by his temperature of the gas and molecules. From experience we successor as professorsuccessorround”. at Uppsala as professor University at Uppsala, the mathematician University, theMårten mathematician Strömer. As Mårten an Strömer. As an know that increasing thermal (heat) interesting aside, itinteresting is worth mentioning aside, it is that worth as mentioningearly as 1743, that P asrofessor early as Christin 1743, Pinrofessor Lyon had Christin in Lyon had energy leads to higher temperatures, built the first mercurybuilt thermometer the first mercury with thethermometer Celsius scale with “the the rightCelsius way scale round” “the. right way round”. and as a rule requires that matter 0 °, boiling point of water 0 ° , boiling point of water 100 °C, boiling point of100 water °C, boiling point of water expands in volume. (Compare with the ideal gas law!) It is therefore not Diagram, left: The 100-degree temperature unreasonable to assume that the scale as used by Anders Celsius. Right: His lowest temperature is to be found successor as professor at Uppsala, Mårten where the so­called animation or Strömer, reversed the scale so that its values increase with the energy level just as we are movement has stopped. This occurs used to seeing it today. at absolute zero, 0 K. To maintain agreement with the already accepted Celsius scale, 100 °, freezing point of100 water °, freezing point of water 0 °C, freezing point of 0water °C, freezing point of water it was decided that 1°C = 1 K = 1/273.16 of the thermodynamic tem­ This law is the starting point of perature at the triple point of water. Avogadro’s temperature scale, We can say that thermodynamic Diagram, left: The Diagram100-RÉAUMURdegree, left temperatur: The 100-degreee scale temperaturas used bye Anders scale as Celsius. used by Right Anderswhich: His Celsius. begins Right at: His absolute zero. temperature scale is defined by one successor as professorsuccessorDuring at Uppsala, as professorthe Mårten same at Strömer, Uppsala, period, reversed Mårten the Strömer,theFrench scale reversedso­ that its theToday values scale so absolute that its values zero is defined as increase with the energyincrease level with just the as energy we are level used just to seeingas we are it today used. to seeing it today. fixed point and one fictive zero point man Réaumur developed his own ­273.15°C. The problem with the gas – absolute zero. The fixed point is the Réaumur Réaumurscale. He also began with the thermometer is that it assumes that triple point of water, which is a state During the same perDuringiodfreezing, the the Frenchman same and period Réaumurboiling, the Frenchman developedpoints Réaumur of his water own developed scale. He alsohisso own began­called scale. He“ideal also began gas” exists.