Calibration temperature scale

Bimetallic materials (thin strips of materials having widely different coefficients of expansion that are bonded together) are used in the form of helical or coil springs that expand or contract with a change in temperature. This change in length is amplified and used to move a pointer over a fixed calibrated temperature scale. Bimetallic strips are also used to open and close contacts with a change of temperature in control devices. 

Analogously to the dynamic method, the energy equivalent of the calorimeter, k.Q, can be obtained by performing calibration experiments in the isothermal mode of operation, using electrically generated heat or the fusion of substances with well-known A us//. Recommendations for the calibration of the temperature scale of DSC instruments for isothermal operation have also been published [254,270]. 

Figure 12. Mbssbauer spectrum of metallic iron at room temperature. Lower diagram shows known energy difference between various resonance peaks used to calibrate velocity scale and indicates the linearity of the velocity as a function of analyzer address...

This temperature is cited to 0.01 °C because it is one of the calibration points on the international temperature scale. 

A temperature scale favored by scientists is the Kelvin scale, named after the British physicist Lord Kelvin (1824—1907). This scale is calibrated not in terms of the freezing and boiling points of water, but rather in terms of the motion of atoms and molecules. On the Kelvin scale, zero is the temperature at which there is no atomic or molecular motion. This is a theoretical limit called absolute zero, which is the temperature at which the particles of a substance... 

Schooley, J. F., Ed., 1982, Temperature—Its Measurement and Control in Science und Industry, Vol. 5, American Institute of Physics, New York. An excellent source of state-of-the-art thermometry comprised of papers from the Sixth International Temperature Symposium. Topics which are covered include temperature scales and fixed points, radiation, resistance, thermocouple, and electronic thermometry, temperature control, and calibration techniques. Preceding volumes in the series date back to 1939. 

Suppose you were dissatisfied with both Celsius and Fahrenheit units and wanted to design your own temperature scale based on ethyl alcohol (ethanol). On the Celsius scale, ethanol has a melting point of — 117.3°C and a boiling point of 78.5°C, but on your new scale calibrated in units of degrees ethanol, °E, you define ethanol to melt at 0°E and boil at 200°E. 

The temperature scale and the cell constant were calibrated using indium. Samples of approximately 4 mg were heated at 20 °C / min over the temperature range of 25-200 °C, under dry nitrogen purging (80 ml /min) in a pin-holed aluminum pan. The melting range of atorvastatin calcium was found to take place over the broad range of 158.4-178.03 °C. 

Temperature scales such as the centigrade scale discussed in Chapter 1 are quite arbitrary, requiring a choice of two calibration points and the material and property used to interpolate between them. We saw that we could alternatively use a single-calibration-point scale based on a broad class of materials—the ideal... 

There are two reasons for having many points with which to fix a temperature scale. One is that, as mentioned before, few materials affected by heat change length equally or linearly. Having many points allows scales to be calibrated in short ranges, where nonlinearity is less likely to have a pronounced effect. The second is that few, if any, thermometers can read all temperatures. Most thermometers are calibrated to read a small range of temperatures. Many fixing points allows for a robust system of calibration. Unfortunately, most of these points require expensive equipment, and even then they are not easy to obtain and/or verify. 

In 1821, Sir Humphrey Davy discovered that as temperature changed, the resistance of metals changed as well. By 1887 H.L. Callendar completed studies showing that purified platinum wires exhibited sufficient stability and reproducibility for use as thermometer standards. Further studies brought the Comitd International des Poids et Measures in 1927 to accept the Standard Platinum Resistance Thermometer (SPRT) as a calibration tool for the newly adopted practical temperature scale. 

All thermometers, regardless of fluid, read the same at zero and 100 if they are calibrated by the method described, but at other points the readings do not usually correspond, because fluids vary in their expansion characteristics. An arbitrary choice could be made, and for many purposes this would be entirely satisfactory. However, as will be shown, the temperature scale of the SI system, with its kelvin unit, symbol K, is based on the ideal gas as thermometric fluid. Since the definition of this scale depends on the properties of gases, detailed discussion of it is delayed until Chap. 3. We note, however, that this is an absolute scale, and depends on the concept of a lower limit of temperature. 

In practice it is the International Practical Temperature Scale of1968 (IPTS-68) which is used for calibration of scientific and industrial instruments-t This scale has been so chosen that temperatures measured on it closely approximate ideal-gas temperatures the differences are within the limits of present accuracy of measurement. The IPTS-68 is based on assigned values of temperature for a number of reproducible equilibrium states (defining fixed points) and on standard instruments calibrated at these temperatures. Interpolation between the fixed-point temperatures is provided by formulas that establish the relation between readings of the standard instruments and values of the international practical temperature. The defining fixed points are specified phase-equilibrium states of pure substances, t a given in Table 1.2. 

Example 1.2 Table 1.3 lists the specific volumes of water, mercury, hydrogen at l(atm), and hydrogen at lOO(atm) for a number of temperatures on the International Practical Temperature Scale. Assume that each substance is the fluid in a thermometer, calibrated at the ice and steam points as suggested at the beginning of this section. To determine how good these thermometers are, calculate what each reads at the true temperatures for which data are given. 

Since the triple point of water is defined to be exactly 273.16 K on the thermodynamic temperature scale, this is an especially important fixed point. It is also a point that can be reproduced with exceptionally high accuracy. If the procedure of inner melting (described below) is used, the temperature of the triple point is reproducible within the accuracy of current techniques (about 0.00008 K). This precision is achieved by using the triple-point cellshov n in Fig. 1. This cell, which is about 7.5 cm in outer diameter and 40 cm in overall length, has a well of sufficient size to hold all thermometers that are likely to be calibrated. ... 

In the following sections, I divide alkenone paleotemperature studies roughly by the time span covered. While arbitrary to some degree, this should allow the reader to gauge the contributions of the alkenone technique to important paleocli-matic questions, which tend to be arrayed by the age and duration of Earth history studied. In addition, studies at different time resolutions will have different sets of supporting information, caveats, and questions to be addressed by future work. Nearly aU of the studies cited rely on the standard Prahl et al. (1988) temperature scale. However, a few applications of nonstandard calibrations exist in the hterature (Pelejero et al., 1999a Wang et al., 1999 Calvo et al., 2002). 

Reaction B used instead of A to minimize bias from calibrations and ionization cross sections Temperature scale adjusted to - 2327 K instead of 2318 K for o-AlgOg. 

Thus, it has been found that the high temperature scale defined by the platinum resistance thermometer calibrated in terms of the melting point of ice, 0°C., the boiling points of water, 100°C., and of sulphur, 444.6°C., at a pressure of 760 mm. Hg.,... 

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