The measurement of temperature

The fundamental meaning of temperature may be described in terms of the zeroth law of thermodynamics. This states that when two bodies are each in thermal equilibrium with a third body they are then in thermal equilibrium with each other, i.e. 

If the temperature is considered to be a linear function of the thermometric property, then  

A temperature measured on one scale can always be converted into a temperature measured on another scale (e.g. Fahrenheit) with mathematical precision (i.e. to as many significant figures as is required—see Section 6.10.1). 

It is important to consider what happens when the substance or property employed is changed. For example, for a liquid in glass thermometer (using the Centigrade scale)  

If linear interpolation is applied in this way then two thermometers using different thermometric properties brought into contact with the same heat reservoir will give identical readings only at the fixed points. 

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Optical metiiods, in both bulb and beam expermrents, have been employed to detemiine tlie relative populations of individual internal quantum states of products of chemical reactions. Most connnonly, such methods employ a transition to an excited electronic, rather than vibrational, level of tlie molecule. Molecular electronic transitions occur in the visible and ultraviolet, and detection of emission in these spectral regions can be accomplished much more sensitively than in the infrared, where vibrational transitions occur. In addition to their use in the study of collisional reaction dynamics, laser spectroscopic methods have been widely applied for the measurement of temperature and species concentrations in many different kinds of reaction media, including combustion media [31] and atmospheric chemistry [32]. 

The measuring of temperature rise permits monitoring efficiency for a fixed pressure ratio and suction temperature. Efficiencies should always exceed 0.6, and 1.00 is approachable in reciprocating devices. Their better efficiency needs to be balanced against their greater cost, greater maintenance, and lower capacity. 

Thermocouple An instrument for the measurement of temperature consisting of two wires of different metals joined at each end. An electrical electromotive force is generated, the magnitude of which allows the temperature to be measured. 

The measurement of temperature is achieved by making use of two experimental facts ... 

Schellenz et al. [ 1.133] confirmed that the assumption of an infinite plate in Eq. (12) is a reasonable approximation, even for drying of products in vials. They show by the measurement of temperature profiles and by X-ray photos during drying of a 5 % mannitol solution, 23 mm filling height, that the sublimation front retreats mostly from the top parallel to the bottom. The heat transfer from glass vials deforms the flat surface only to some extent close to the wall. 

The measurement of temperature is also delayed by a sensor lag given by... 

A non-invasive infrared (IK) method has been developed for the measurement of temperatures of small moving fuel droplets in combustion chambers. 7111 The IR system is composed of two coupled off-axis parabolic mirrors and a MCT LWIR detector. The system was used to measure the temperature variations in a chain of monosized droplets generated with equal spacing and diameter (200 pm), moving at a velocity of >5 m/s and evaporating in ambient air. The system was also evaluated for droplet temperature measurements in flames under combustion conditions. 

Hamilton Umicon Lumicon chemi- and biolumium assay luminometer This equipment is used in test-tube scale luminescent immunoassays. With its sample compartment (thermostatted by means of Peltier elements, which allow the temperature to be set from 15°C to 40°C with a precision of 0.1°K) this instrument is suitable for the measurement of temperature-sensitive bioluminescence resulting from enzymic reactions and also in phagocyte-mediated luminescence measurements. 

The measurement of temperature is necessary for the calibration of most probes like blood oxygen, pH, ions, voltage, and carbon dioxide sensors. The use of optical methods to invasively measure physiological temperature has the advantage of electrical isolation, when compared to traditional approaches like the use of thermocouplers. 

Although the change in state of the heat bath, hence the value of Q, usually is determined by measuring a change in temperature, this is a matter of convenience and custom. For a pure substance the state of a system is determined by specifying the values of two intensive variables. For a heat bath whose volume (and density) is hxed, the temperature is a convenient second variable. A measurement of the pressure, viscosity, or surface tension would determine the state of the system equally as well. This point is important to the logic of our development because a later dehnition of a temperature scale is based on heat measurements. To avoid circularity, the measurement of heat must be independent of the measurement of temperature. 

First, the temperature changes. The mean environmental temperature is readily accessible, but data for the past are to be taken with prudence since the measurement of temperature is a recent acquisition. Indirect evidence (Fig. 16.2.3.1) suggests that the Little Ice Age, which lasted from the end of the Middle Ages until the mid 19 century, was colder than now (0.5 C). Such conclusions derive mainly from the analysis of proxies, which are geographically scattered indicators, in the form of both natural (physical and biological) and documentary (written) archives for the last millenniiun... 

Taylor (1952), 43 (Equation for die temp of expln) 59, Table 14 (Approximate relations of temps of expln to heats of expln) 33) F.S. Harris Jr, The Measurement of Temperature in Explosives , Univ of Utah Tech Mem (Aug 31, 1953) (A literature survey giving a summary of methods of measuring temps developed on deton of expls) 34) J.H. Hett J.B. Gilstein, A Study of Techniques for the Measurement of Detonation Spectra and Temperatures , ResDiv of NYUniv, Final Rept May 14, 1953. Contract DA-30-069-ORD-945 35) J.B. Conway et al, JACS 77, 2026-27 (1955) (The production of a flame temp of 5000°K) 36) F.C. Gibson C.M. Mason,... 

A.S. Leah N. Carpenter, "The Estimation of Atomic Oxygen in Open Flames and the Measurement of Temperature , 4thSymp-Combstn (1953), pp 274—85(27 refs)... 

The parameter x corresponds to the chemical composition, since Y in the notation MXy is equal to 8/(4 4- x). a is the ratio of the inter-layer to intra-layer vacancy-vacancy interaction and t is the measure of temperature. 

Recent work on spatial stabilization has been directed towards the production of one-dimensional flames (Fll, P10). These may be either flat, cylindrical, or spherical. The primary purpose of such flames has been to measure velocities accurately and to provide a flame that can be described by a one-dimensional theory. The measurement of temperature and composition profiles is meaningful, of course, only in a flame in which the geometry is known. One-dimensional geometry greatly reduces the labor required to analyze such profiles in order to study kinetics. 

In this section we refer to E rather than its dimensionless counterpart = E, since it seems advisable to make the measure of temperature P = 1/k.T explicit. 

The measurements of temperature and species concentrations profiles in premixed, laminar flames play a key role in the development of detailed models of hydrocarbon combustion. Systematic comparisons are given here between a recent laminar methane-air flame model and laser measurements of temperature and species concentrations. These results are obtained by both laser Raman spectroscopy and laser fluorescence. These laser probes provide nonintrusive measurements of combustion species for combustion processes that require high spatial resolution. The measurements reported here demonstrate that the comparison between a model and the measured concentrations of CH, O2,... 

The measurement of temperature is a measurement of energy and therefore has different measurement characteristics than other properties. The primary difference in temperature measurement is that it is not cumulative. You can take two different meter sticks and place them end to end to measure something longer than one meter. The comparable action can be made for the measurement of mass. 

For the remarkable rise in tension sometimes found with increasing temperature there is no satisfactory explanation as yet there is no reasonable doubt of the fact, although quantitatively the measurement of temperature coefficients is so difficult that there is often considerable 1 J.A.CJS. (1921), 1621. See Chap. Ill, 9. 

Some information on crystal electric field levels can be obtained from the measurement of temperature-dependent Van Vleck susceptibility which can be described by the relationship... 

Practical difficulties arise in making very precise determinations of temperature on the thermodynamic scale the precision of the more refined thermometric techniques considerably exceeds the accuracy with which the experimental thermometer scale may be related to the thermodynamic scale. For this reason, a scale known as the International Temperature Scale has been devised, with several fixed points and with interpolation formulas based on practical thermometers (e.g., the platinum resistance thermometer between 13.803 K and 1234.93 K). This scale is intended to correspond as closely as possible to the thermodynamic scale but to permit more precision in the measurement of temperatures. Further details about this scale are given in Chapter XVII. 

Fixed points for the calibration of the optical pyrometers are the silver, gold, and copper points and higher temperature secondary fixed points such as those given in Table 2. Calibration at other temperatures can be accomplished by use of a rotating sector or a filter of accurately known transmission factor between the fixed-point source and the pyrometer, in order to simulate a source of lower temperature in accordance with the Planck equation. Such sectors or filters are used also to permit the optical pyrometer to be used for the measurement of temperatures much above 2000 K. 

The expansion on heating is most marked in the case of gases, and was noticed first in them as early as 100 b.c., we find this property of gases made use of by Hero of Alexandria in some ingenious experiments. In the case of liquids and solids the expansion is much less noticeable in the latter case it is even somewhat difficult to determine. Gases and liquids are most suitable for the measurement of temperature, and for the construction of temperature measuring instruments, or thermometers, as they are called. 

The instruments used in the measurement of temperature may be divided into five classes, namely ... 

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