techniques for approximating the international temperature ... - BIPM

More documents

Recommendations

Info

90 For a group of 45 thermometers having W68(H20 b.p.) > 1.3925, Bedford (1972b) showed that if the thermometers were calibrated only at the triple and boiling points of water and if a common value of B were assumed for every thermometer, then the extrapolated temperatures (Te) diverge smoothly from T68 (or T90) by up to 1 K at 100 K, 1.7 K at 70 K, and -12 K near 20 K, and variations in these temperatures are small (Fig. 6.1). Using a tabulated or functional correction, one can measure T68 (and, consequently, T90 using the tables of Appendix A) to within ± 3 mK down to 150 K, ± 15 mK at 77 K, and ± 30 mK at 30 K. We note that: (i) The method is simple. The thermometers are calibrated only at the triple and boiling points of water. If B were measured by a tin-point or zinc-point calibration, the extrapolated scale uncertainty might be marginally smaller. This would be feasible for a long-stem thermometer but not for many capsule thermometers. (ii) The procedure is equally valid for capsule or long-stem PRTs. (iii) There is no definitive test of the extrapolation; there is a high probability, but no certainty, that any particular PRT will fall within the uncertainties quoted. (b) Another simple secondary realization for the range 90 K to 273 K uses only two fixed points and obtains a third from an experimentally-observed linear correlation between W(O2 b.p.) and W(H20 b.p.). This correlation was first pointed out by Brodskii (1968), who found the following relation for thermometers with W68(H20 b.p.) > 1.3920: W(O2 b.p.) = a1 + b1 (W(H20 b.p.) -1) . (8.3) Berry [(1963), (1972)] examined similar correlations in detail. For platinum of the highest available purity, he determined [Berry (1972)] a linear relation of the form of Eq. (8.3) corresponding to various equilibrium concentrations of quenched-in vacancies. This is shown as curve V in Fig. 8.2, which Berry suggested would be an upper bound for all real PRTs. Similarly, his curve L [Berry (1963)] approximates the mean behaviour for his large group of thermometers. From Fig. 9 of Berry (1963) one can deduce a lower bound (curve M) below which no SPRT is likely to lie.
91 Fig. 8.1: Differences from T90 of temperatures Te extrapolated below 0 °C using the IPTS-68 defining equations for above 0 °C. The hatched area shows the maximum observed deviations ∆(T90 - Te) in (T90 - Te) for a group of 45 thermometers [Bedford (1986)]. Fig. 8.2: Linear relationships between W(O2 b.p.) and W(H20 b.p.) for platinum: B, after Brodskii (1968); V, ideally pure platinum [Berry (1972)]; L, mean of many thermometers [Berry (1963)]; M, lower bound for SPRT [Berry (1963)]; S, result when argon replaces oxygen, converted to oxygen [Seifert (1980), (1984)]; [Bedford (1986)].
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 and 20:
xviii 11.3 Thermal Contact 111 11.4
Page 21 and 22:
1 1. Introduction The Comité Consu
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
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 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 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
Page 150 and 151: 130 Fig. 16.1: (a) Fabrication of I
Page 152 and 153: 132 capillaries of a twin- (or four
Page 154 and 155: 134 advised to choose the thermomet
Page 156 and 157: 136 Fig. 16.6: Distribution of the
Page 158 and 159: 138 and between different thermomet
Page 160 and 161:
140 therefrom) can then be used wit
Page 162 and 163:
142
Page 164 and 165:
144 Fig. 16.8: Tolerances for indus
Page 166 and 167:
146 Stability on thermal cycling is
Page 168 and 169:
18.2.1 Type T Thermocouple 148 With
Page 170 and 171:
150 within ± 0.5 to 0.7 percent. T
Page 172 and 173:
152 insulation even though it be af
Page 174 and 175:
154 Table 18.4: Recommended Sheath
Page 176 and 177:
156 In the case of the Types K and
Page 178 and 179:
158 temperature is measured with th
Page 180 and 181:
160 19. Thermometry in Magnetic Fie
Page 182 and 183:
162 Type of Sensor T(K) Magnetic Fl
Page 184 and 185:
164 be noted that these lower tempe
Page 186 and 187:
166 Fig. 19.2: The change in calibr
Page 188 and 189:
168 Carbon-glass thermometers (Chap
Page 190 and 191:
Ancsin, J. and Phillips, M.J. (1984
Page 192 and 193:
172 Berry, R.J. (1972): The Influen
Page 194 and 195:
174 Brodskii, A.D. (1968): Simplifi
Page 196 and 197:
176 Crovini, L., Perissi, R., Andre
Page 198 and 199:
Hudson, R.P. (1972): Principles and
Page 200 and 201:
180 Lengerer, B. (1974): Semiconduc
Page 202 and 203:
182 OIML (1985): International Reco
Page 204 and 205:
184 Rusby, R.L. (1975): Resistance
Page 206 and 207:
186 Seifert, P. and Fellmuth, B. (1
Page 208 and 209:
188 Ween, S. (1968): Care and Use o
Page 210 and 211:
190 Fig. A.1: Differences between t
Page 212 and 213:
National Institute of Metrology P.O
Page 214 and 215:
194 Appendix C Some Suppliers of Va
Page 216 and 217:
196 Appendix D Calculations Relativ
Page 218 and 219:
198 4. The calculation of the numbe
Page 220 and 221:
200 Appendix F Interpolation Polyno
Page 222 and 223:
- temperature range from 0 °C to 1
Page 224 and 225:
204 where: d0 = 0; d5 = -3.17578007
show all

techniques for approximating the international temperature ... - BIPM

Create successful ePaper yourself

Delete template?

Save as template?