techniques for approximating the international temperature ... - BIPM

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80 into the bulb (hydrous ferric oxide). It should be enclosed in a metallic mesh to avoid its dispersing to the walls during boiling. The quantity of catalyst is not important (e.g. 0.15 g) but it is inefficient if it is not in good contact with the liquid phase. There are similar problems with deuterium, which is more easily contaminated, and always contains some hydrogen deuteride (HD) even after the most careful preparation. HD will also be formed in measurable quantities (over 1%) from hydrogen atoms that diffuse from the bulk of the container or, more commonly, from exchange with H2O if a hydrated catalyst is used. Errors of several hundredths of a kelvin may arise near 18.7 K [Pavese and McConville (1987)]. c. Neon [Ancsin (1978), Furukawa (1972), Tiggelman et al. (1972), Tiggelman (1973)] The volatile impurities, H2 and He, are not soluble in the liquid phase and do not influence the vaporization curve. Their presence in the vapour phase causes a decrease in the boiling temperature of Ne. Their effect can be minimized by increasing the volume of the vapour phase [Ancsin (1978)]. Most of the possible nonvolatile impurities have small partial pressures below 27 K and are trapped somewhere in the tube. Only nitrogen has a notable influence. The limit of solubility of N2 in Ne is 150 ppmv*. The triple point temperature of saturated Ne is 2.25 mK lower than for pure Ne. For a mixture with 1000 ppmv* of N2, the vapour pressure is lowered by 100 to 300 Pa, giving a boiling temperature 6 to 10 mK higher than pure Ne between 24.562 K and 27.102 K. It appears that the isotopic constitution of natural neon varies so little from one supplier to another that there is no need to be concerned with variations in it. Natural neon as described in "Supplementary Information for the ITS-90" [CCT (1990)] is composed of 90.5% of 20 Ne, 0.27% of 21 Ne, and 9.2% of 22 Ne. The 21 Ne is in too small a quantity to influence the results, but this is not the case for 22 Ne and 20 Ne which have different boiling and triple points: the latter are 24.546 K and 24.687 K respectively (corresponding to a pressure difference of 326 Pa). An increase of the concentration of 20 Ne by 0.1% increases the normal boiling point by 0.13 mK. There also exists an isotopic composition difference between the liquid and vapour phases. The molar concentration of 22 Ne is higher in the liquid phase than in the vapour phase by 0.3% at the boiling point and 0.4% at the triple point [Furukawa (1972)]. This _________________________________________________________________________ * The abbreviation ppmv is used to mean an impurity content of one part by volume of solute per 10 6 parts by volume of solvent.
81 creates an uncertainty of 0.4 mK in the value of the normal boiling point depending upon whether the ITS composition applies to the liquid or the vapour phase. In the absence of a precise analysis, the error can be minimized if the volume of the liquid phase is much larger than that of the vapour phase. d. Nitrogen [Ancsin (1974a)] For nitrogen in the liquid phase, volatile impurities such as He, H2, and Ne, if present, stay entirely in the vapour phase and have no detectable effect on the temperature of the boiling liquid. Non-volatile impurities such as O2 and Ar lower the triple point value, while CO and (especially) Kr raise it. Impurities have a complex effect on the whole vapour pressure relationship, which cannot simply be represented as a shift proportional to the temperature changes at the triple and normal boiling points (Fig. 6.11). There is a consequent change of all the constants in the vapour pressure equation. e. Argon [Ancsin (1973b)] As impurities, He, Ne, and H2 have no influence; N2 (volatile) decreases the temperature of the dew point by more than 2 mK for 100 ppmv. Oxygen (nonvolatile) has no influence if the concentration is less than 200 ppmv, whereas CH4 and Kr (nonvolatiles) increase the dew point temperature by approximately 2 mK for 100 ppmv. f. Oxygen [Ancsin (1973a, 1974b), Tiggelman (1973), Compton and Ward (1976), Kemp et al. (1976)] Since the principal impurities are volatile it is necessary to use a well-filled bulb. Helium and neon are not soluble in liquid oxygen. For a concentration of 1 ppmv, nitrogen decreases the boiling (condensation) point temperature by 19 µK; krypton increases it by 5.6 µK; argon decreases it by approximately 5 µK. The influence of H2O and CO2 is imperceptible up to a concentration of 100 ppmv. As observed with nitrogen, the effect of the impurities on the whole vapour pressure curve is highly non-linear, and therefore distorts the whole vapour pressure equation (Fig. 6.12) [Ancsin (1974b)]. Some of the discrepancies observed in the literature between different vapour pressure scales can be attributed to this effect. The isotopic effects in oxygen are perceptible only when the volume of residual liquid is small. The vapour pressure of pure 18 O is about 1.5% less than that of the "normal" mixture; the associated correction is about 11 µK at the boiling point for an isotopic composition of 0.210% instead of 0.204% [Tiggelman and Durieux (1972b)].
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BUREAU INTERNATIONAL DES POIDS ET M
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TECHNIQUES FOR APPROXIMATING THE IN
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iv W(100 °C) = 1.385 (exact value
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Centre for Quantum Metrology Nation
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2. Type J viii a) temperature range
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c) temperature range from 1664.5 °
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xii
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xiv Acknowledgments This monograph
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xvi 3.3.2 Melting Points of Gold (1
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xviii 11.3 Thermal Contact 111 11.4
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1 1. Introduction The Comité Consu
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3 thermometers except in special ex
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5 The accuracies with which tempera
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Table 1.1: Summary of Some Properti
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PART 1: TECHNIQUES AND THERMOMETERS
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11 Fig. 2.1: One form of apparatus
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13 Fig. 2.3: Flow cryostat, shown w
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15 Fig. 2.4: Stirred liquid bath fo
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17 contained within a cylindrical c
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19 Fig. 2.5: Schematic drawing of a
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21 device SRM 767 [Schooley et al.
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23 Table 3.1 : Current Best Estimat
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25 The widely-used, but not very re
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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
Page 70 and 71: 50 Fig. 4.6: Effect of a radio-freq
Page 72 and 73: 52 that it will not be subject to m
Page 74 and 75: ln R n = ∑ i= 0 54 ⎛ ln T - P
Page 76 and 77: 56 Fig. 5.1: Resistance (Ω) and s
Page 78 and 79: 58 thermometer wires) caused a more
Page 80 and 81: 60 6. Vapour Pressure Thermometry*
Page 82 and 83: 62 transitions, but it could be app
Page 84 and 85: n ∑ i= 2 64 L x [ Π − k ] P =
Page 86 and 87: 66 Fig. 6.3: Diagram at constant pr
Page 88 and 89: 68 Fig. 6.4: Schematic construction
Page 90 and 91: 70 Fig. 6.6: Use of an evacuated ja
Page 92 and 93: 72 Following this, the connecting t
Page 94 and 95: 74 Fig. 6.9: (c) N2, CO, Ar, O2, CH
Page 96 and 97: 76 the Weber-Schmidt equation [Webe
Page 98 and 99: 78 Table 6.1: Temperature values (K
Page 102 and 103: 82 Fig. 6.12: Effect on the vapour
Page 104 and 105: 84 the remaining liquid increases.
Page 106 and 107: 86 Curie constant (C⊥ is about 0.
Page 108 and 109: 8.1 General Remarks 88 8. Platinum
Page 110 and 111: 90 For a group of 45 thermometers h
Page 112 and 113: 92 More recently, Seifert [(1980),
Page 114 and 115: 94 For thermometers with W(4.2 K) <
Page 116 and 117: 96 after 500 h at 1700 °C in air,
Page 118 and 119: 98 normally extends about 50 cm bac
Page 120 and 121: 100 inhomogeneities result from the
Page 122 and 123: 9.5 Approximations to the ITS-90 10
Page 124 and 125: 104 10. Infrared Radiation Thermome
Page 126 and 127: 106 almost negligible. The final ac
Page 128 and 129: 108 11. Carbon Resistance Thermomet
Page 130 and 131: 110 Fig. 11.1: Resistance-temperatu
Page 132 and 133: 112 Table 11.1: Typical Time Consta
Page 134 and 135: 114 calibration after each cool-dow
Page 136 and 137: 116 12. Carbon-Glass Resistance The
Page 138 and 139: 118 Fig. 12.1: Resistance-temperatu
Page 140 and 141: 120 14. Diode Thermometers Diodes c
Page 142 and 143: 122 2 BT V = E0 − − CT ln ( DT)
Page 144 and 145: 124 Fig. 15.1: Principal features o
Page 146 and 147: 126 For a thermometer graduated abo
Page 148 and 149: 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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