techniques for approximating the international temperature ... - BIPM
techniques for approximating the international temperature ... - BIPM techniques for approximating the international temperature ... - BIPM
Table 1.1: (Continued) Usual Thermometric Typical Thermometer Temperature Quantity Uncertainty Range 8 Thermistor -80 °C to elec. resist.* 0.1 K (much better 250 °C if use confined to very small temperature range) Platinum: SPRT 14 K to 630 °C elec. resist.* 0.5 mK IPRT 20 K to 600 °C 50 mK Radiation 100 °C to 3000 °C spectral radiance 1 K < 1000 °C of source 5 K > 1000 °C _________________________________________________________________________ * elec. resist. is the electrical resistance
PART 1: TECHNIQUES AND THERMOMETERS FOR APPROXIMATING THE INTERNATIONAL TEMPERATURE SCALE OF 1990 9 The most common and best-characterized thermometers for very low temperature use are those that relate temperature to electrical resistance. In Part 1 there is a discussion of germanium, rhodium-iron, and platinum resistance thermometers together with their associated calibrations and interpolation formulae for approximating the ITS-90. The use of germanium is normally restricted to below 30 K. The same has been true for rhodium-iron although the chief reason for not using it to near 300 K has been competition from platinum. With platinum, calibration at a few fixed points coupled with simple interpolation will reproduce the ITS-90 moderately accurately. Germanium and rhodium-iron thermometers, on the other hand, must be individually calibrated because no two thermometers of the same type have exactly similar resistance/temperature characteristics, and there must be calibration at many points because interpolation of the resistance/temperature relationship is difficult. They are used as transfer standards for maintaining the ITS-90 below about 25 K, defined in terms of thermodynamic thermometry. Germanium resistance thermometers are small, relatively inexpensive, and very sensitive at the lower end of their range. Standard-type rhodium-iron resistance thermometers are much larger, much more expensive and less sensitive than germanium, but are more stable and have a wider range of use. Platinum costs the same as, or more than, rhodium-iron, and is the clear choice above about 25 K. Both platinum and rhodiumiron are extremely stable; with proper handling, which means treating the thermometers as fragile and not subjecting them to mechanical shocks or vibrations, variations as large as a millikelvin are unusual. Germanium thermometers are about an order of magnitude less stable. Vapour pressure thermometry and magnetic thermometry are also discussed in Part 1 because of their fundamental use. No comparable treatment of the former appears to exist. Platinum thermocouples and infrared radiation thermometers are also included in Part 1 because they are widely used to approximate the ITS-90. The discussion of these various thermometers is preceded by a description of the methods, and hence of cryostats, baths, and furnaces, for attainment of uniform temperature environments (Chapter 2) and by some discussion of fixed points (Chapter 3), the latter intended to complement, rather than duplicate, that in "Supplementary Information for the ITS-90" [CCT (1990)].
- 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: Table 1.1: Summary of Some Properti
- 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
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Table 1.1: (Continued)<br />
Usual Thermometric Typical<br />
Thermometer Temperature Quantity Uncertainty<br />
Range<br />
8<br />
Thermistor -80 °C to elec. resist.* 0.1 K (much better<br />
250 °C if use confined to very<br />
small <strong>temperature</strong> range)<br />
Platinum: SPRT 14 K to 630 °C elec. resist.* 0.5 mK<br />
IPRT 20 K to 600 °C 50 mK<br />
Radiation 100 °C to 3000 °C spectral radiance 1 K < 1000 °C<br />
of source 5 K > 1000 °C<br />
_________________________________________________________________________<br />
* elec. resist. is <strong>the</strong> electrical resistance
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