techniques for approximating the international temperature ... - BIPM

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xix 18.3.2 Sheaths 150 18.3.3 Protection Tubes 152 18.3.4 Thermocouple Construction 152 18.3.5 Circuit Construction 153 18.4 Annealing of the Thermoelements 155 18.5 Guidelines for Proper Handling and Use -Installation and Sources of Errors 156 18.6 Calibration of Base-Metal Thermocouples 158 19. Thermometry in Magnetic Fields 160 20. References 169 Appendices A. Differences between the ITS-90 and the EPT -76, and between the ITS-90 and the IPTS-68 189 B. Addresses of National Standards Laboratories 191 C. Some Suppliers of Various Cryogenic Thermometers 194 D. Calculations Relative to the Filling of a Vapour Pressure Thermometer 196 E. Calculation of the Aerostatic Pressure Correction for a Vapour Pressure Thermometer 199 F. Interpolation polynomials for Standard Thermocouple Reference Tables 200
1 1. Introduction The Comité Consultatif de Thermométrie (CCT) has always had as its chief concern the perfecting of the International Temperature Scale (ITS) and, consequently, has been occupied with thermometric measurements of the very highest accuracy. There are many laboratories in the world, including even some of the national standardizing laboratories in countries adhering to the Convention du Metre, that, while requiring temperature measurements to be related to the ITS, do not require this ultimate accuracy. In an attempt to address this need, the CCT assigned to a Working Group the task of preparing a monograph describing methods for approximating the ITS that are simpler and more practicable than the fundamental definition, giving estimated accuracies of the various approximations. That the need for this information is high can be inferred from the result of a study in the U.S.A. [Frost and Sullivan (1984)] which reveals that temperature is the most commonly measured physical variable today. The study forecast annual expenditures in the U.S.A. of $0.9 x 10 9 on temperature measurement and control devices and instrumentation by 1988 for a real annual growth rate of 10% in the industrial temperature instrumentation market over a 5-year span. This monograph is meant to be a companion to "Supplementary Information for the ITS-90" [CCT (1990)], a forthcoming revision of "Supplementary Information for the IPTS-68 and the EPT- 76" [CCT (1983)]. The latter is directed to those who wish to realize the ITS-90 with accuracies ranging from moderately high to the very highest level; the present monograph is to give guidance to those who wish to approximate the ITS-90 using simpler techniques and for whom those levels of accuracy are unnecessarily high. It is clear that in such a monograph care must be taken to emphasize that the approximations described do not constitute official recipes for realizing the ITS-90, different from but less accurate than the fundamental definition. Such a proliferation of "official" scales would be highly undesirable. This monograph therefore provides information on how one can approximate the ITS- 90 to a modest but specified level of accuracy with a variety of techniques. It necessarily includes considerable discussion of the sensors themselves - their properties, reliability and limitations, and guidelines for proper handling and use - but this discussion is in no way exhaustive. A large literature already exists on these sensors to which the reader is referred for extensive treatments.
Page 1 and 2: BUREAU INTERNATIONAL DES POIDS ET M
Page 3 and 4: TECHNIQUES FOR APPROXIMATING THE IN
Page 5 and 6: iv W(100 °C) = 1.385 (exact value
Page 7 and 8: Centre for Quantum Metrology Nation
Page 9 and 10: 2. Type J viii a) temperature range
Page 11 and 12: c) temperature range from 1664.5 °
Page 13 and 14: xii
Page 15 and 16: xiv Acknowledgments This monograph
Page 17 and 18: xvi 3.3.2 Melting Points of Gold (1
Page 19: xviii 11.3 Thermal Contact 111 11.4
Page 23 and 24: 3 thermometers except in special ex
Page 25 and 26: 5 The accuracies with which tempera
Page 27 and 28: Table 1.1: Summary of Some Properti
Page 29 and 30: PART 1: TECHNIQUES AND THERMOMETERS
Page 31 and 32: 11 Fig. 2.1: One form of apparatus
Page 33 and 34: 13 Fig. 2.3: Flow cryostat, shown w
Page 35 and 36: 15 Fig. 2.4: Stirred liquid bath fo
Page 37 and 38: 17 contained within a cylindrical c
Page 39 and 40: 19 Fig. 2.5: Schematic drawing of a
Page 41 and 42: 21 device SRM 767 [Schooley et al.
Page 43 and 44: 23 Table 3.1 : Current Best Estimat
Page 45: 25 The widely-used, but not very re
Page 48 and 49: 28 fraction of sample melted) can g
Page 50 and 51: 30 Fig. 3.2a: Apparatus for the cal
Page 52 and 53: 32 Fig. 3.3: Sealed cell for realiz
Page 54 and 55: 34 Final readings of the thermomete
Page 56 and 57: 36 temperatures differ (usually) sy
Page 58 and 59: 38 Fig. 3.4: Cross sectional drawin
Page 60 and 61: 40 Fig. 3.5: Miniature graphite bla
Page 62 and 63: 42 4. Germanium Resistance Thermome
Page 64 and 65: 44 Fig. 4.3: Example of the Π-type
Page 66 and 67: 46 Fig. 4.4: Differences between dc
Page 68 and 69: 48 - conversely, p-doped thermomete
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50 Fig. 4.6: Effect of a radio-freq
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52 that it will not be subject to m
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ln R n = ∑ i= 0 54 ⎛ ln T - P
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56 Fig. 5.1: Resistance (Ω) and s
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58 thermometer wires) caused a more
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60 6. Vapour Pressure Thermometry*
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62 transitions, but it could be app
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n ∑ i= 2 64 L x [ Π − k ] P =
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66 Fig. 6.3: Diagram at constant pr
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68 Fig. 6.4: Schematic construction
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70 Fig. 6.6: Use of an evacuated ja
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72 Following this, the connecting t
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74 Fig. 6.9: (c) N2, CO, Ar, O2, CH
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76 the Weber-Schmidt equation [Webe
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78 Table 6.1: Temperature values (K
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80 into the bulb (hydrous ferric ox
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82 Fig. 6.12: Effect on the vapour
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84 the remaining liquid increases.
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86 Curie constant (C⊥ is about 0.
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8.1 General Remarks 88 8. Platinum
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90 For a group of 45 thermometers h
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92 More recently, Seifert [(1980),
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94 For thermometers with W(4.2 K) <
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96 after 500 h at 1700 °C in air,
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98 normally extends about 50 cm bac
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100 inhomogeneities result from the
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9.5 Approximations to the ITS-90 10
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104 10. Infrared Radiation Thermome
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106 almost negligible. The final ac
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108 11. Carbon Resistance Thermomet
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110 Fig. 11.1: Resistance-temperatu
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112 Table 11.1: Typical Time Consta
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114 calibration after each cool-dow
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116 12. Carbon-Glass Resistance The
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118 Fig. 12.1: Resistance-temperatu
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120 14. Diode Thermometers Diodes c
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122 2 BT V = E0 − − CT ln ( DT)
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124 Fig. 15.1: Principal features o
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126 For a thermometer graduated abo
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128 rise decreases with time but in
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130 Fig. 16.1: (a) Fabrication of I
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132 capillaries of a twin- (or four
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134 advised to choose the thermomet
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136 Fig. 16.6: Distribution of the
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138 and between different thermomet
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140 therefrom) can then be used wit
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142
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144 Fig. 16.8: Tolerances for indus
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146 Stability on thermal cycling is
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18.2.1 Type T Thermocouple 148 With
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150 within ± 0.5 to 0.7 percent. T
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152 insulation even though it be af
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154 Table 18.4: Recommended Sheath
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156 In the case of the Types K and
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158 temperature is measured with th
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160 19. Thermometry in Magnetic Fie
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162 Type of Sensor T(K) Magnetic Fl
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164 be noted that these lower tempe
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166 Fig. 19.2: The change in calibr
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168 Carbon-glass thermometers (Chap
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Ancsin, J. and Phillips, M.J. (1984
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172 Berry, R.J. (1972): The Influen
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174 Brodskii, A.D. (1968): Simplifi
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176 Crovini, L., Perissi, R., Andre
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Hudson, R.P. (1972): Principles and
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180 Lengerer, B. (1974): Semiconduc
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182 OIML (1985): International Reco
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184 Rusby, R.L. (1975): Resistance
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186 Seifert, P. and Fellmuth, B. (1
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188 Ween, S. (1968): Care and Use o
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190 Fig. A.1: Differences between t
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National Institute of Metrology P.O
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194 Appendix C Some Suppliers of Va
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196 Appendix D Calculations Relativ
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198 4. The calculation of the numbe
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200 Appendix F Interpolation Polyno
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- temperature range from 0 °C to 1
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204 where: d0 = 0; d5 = -3.17578007
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