techniques for approximating the international temperature ... - BIPM

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76 the Weber-Schmidt equation [Weber et al. (1936)], although also the experimental tables of Roberts and Sydoriak (1956), or the calculation of Bennett and Tompkins (1957) can be used for the two helium isotopes. The Weber-Schmidt equation is P ln P 1 2 where = 1 T1 ln 2 T 2 + y = 0. 18131ln X RP y y 1 2 + + ( ) n 1+ T / 273. 1 0. 1878 0. 1878 X = 1.8087, n = 0.147 for helium, + 0. 41284 ln X = 1.1470, n = 0.195 for hydrogen. y y 1 2 + 1. 8311 − + 1. 8311 0. 15823 ln y y 1 2 + + 4. 9930 4. 9930 Index 1 indicates the hot end of the tube, index 2 the cold end; R designates the tube radius in cm, P the pressure in Pa, and T the temperature in K. al. (1982)]. The trend of the effect is shown in Fig. 6.10 [Roberts and Sydoriak (1956), Durieux et Some temperature values for a vapour pressure thermometer using He or H2 are shown in Table 6.1 With oxygen, the correction reaches 20 mK near 54 K (when P = 100 Pa), but it is already less than 0.05 mK at 64 K for an Inconel tube 1.6 mm in diameter [Tiggelman (1973)]. For neon near 20 K it is less than 1 mK [Tiggelman (1973)]. In general, these calculations can be 10% to 25% in error [McConville et al. (1966) and McConville (1972)], since the correction depends upon the material used for the tube and the physico-chemical conditions of its inner surface, which may also vary with time. They can be calculated [McConville et al. (1966)] as a function of the reflection coefficient of the tube but, unfortunately, the latter is never well known and may change after long exposure to the gas. The thermomolecular effect can be measured with an additional tube [Berry (1979)]. Another solution, which eliminates the correction, is to use a diaphragm transducer located in the lower temperature region [Gonano and Adams (1970)] (see Fig. 6.7). Current practice consists of using pressure tubes of the largest section possible compatible with keeping heat transfer losses reasonably small (and to include some means of blocking radiation (gains, not losses) and damping oscillations). If the calculated correction is to be realistic, it is indispensable to have a constant diameter in the parts of the tube where the temperature is ill-defined. The two corrections from Secs. 6.3.4 and 6.3.5 are usually small and in many cases the only significant uncertainty is that due to the reading of the pressure.
77 Fig. 6.10: Ratios of thermo molecular pressures for 3 He and 4 He (R, radius of tube in centimetres; pF and pc, pressure in Pa at the cold (TF) and hot (Tc) extremities of the tube) [Roberts and Sydoriak (1956)]. Fig. 6.11: The observed lowering of the vapour pressure of N2 by nonvolatile impurities, as a function of the vapour pressure of pure N2. Curve A, N2:100 ppmv. CO; curve B, N2:100 ppmv. Ar; curve C, N2:100 ppmv. Kr; curve D, N2:100 ppmv. O2 [Ancsin (1974a)].
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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
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
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 98 and 99: 78 Table 6.1: Temperature values (K
Page 100 and 101: 80 into the bulb (hydrous ferric ox
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
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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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