摘要:

On the occasion of the 8thInternational Temperature Symposium, we present a brief overview of the impact on industry of temperature metrology conducted at the National Institute of Standards and Technology (NIST), other national metrology institutes (NMIs), and industrial laboratories. A number of historical examples from the past hundred years illustrate the process of research, development, and commercialization of new technologies for temperature measurement and control. Several promising directions of future research are also discussed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627091

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

For several years Physikalisch‐Technische Bundesanstalt (PTB) has performed thermodynamic temperature measurements on a large area blackbody applying filter radiometers (FR) based on silicon photodiodes and interference filters with center wavelengths at 676 nm, 800 nm, 900 nm, and 1000 nm. These FRs were used for the determination of possible systematic deviations of temperatures measured according to the International Temperature Scale of 1990 (ITS‐90),T90, and the thermodynamic temperaturesT. The measurements in 1995 with the 676‐nm‐FR and the 800‐nm‐FR revealed a difference of 50 mK ofT−T90at temperatures around the freezing point of silver (961.78 °C). The observed difference decreases with decreasing temperatures, indicating that it may be attributed to a systematic deviation in the ITS‐90 fromTdue to the gas thermometric temperature measurement at 457 °C, which has been used as a reference temperature for extrapolation of the ITS‐90 to higher temperatures. For a further, more detailed investigation it was necessary to measure the differenceT−T90down to temperatures of 420 °C, the temperature of freezing zinc, which serves as one of the temperature fixed points of the ITS‐90. However, the spectral responsivity of silicon photodiodes does not allow their application in filter radiometers with center wavelengths beyond 1000 nm, which are needed for accurate thermodynamic temperature measurements below 450 °C. Therefore a filter radiometer with center wavelength arround 1600 nm based on an Indium‐Gallium‐Arsenide photodiode has been developed. The design of this radiometer, the assessment of its spectral responsivity and its temperature dependence is shown.T−T90results are presented for the temperature range from 400 °C to 600 °C obtained with filter radiometers with their center wavelengths at 800 nm, 900 nm, 1000 nm, and 1600 nm. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627092

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The thermodynamic temperature of the freezing point of copper was measured by noise thermometric methods. A conventional approach was used which combines the noise voltage of the measuring resistor with that of a reference resistor maintained at a known temperature. Besides this comparison method the thermometer is characterized by a two‐channel arrangement to eliminate parasitic noise of electronic components by cross correlation. The thermodynamic temperature measured at the freezing point of copper amounts to a value of 1084.54 °C ± 0.12 °C (k= 2). This corresponds to the value of the ITS‐90 temperature of this fixed point of 1084.62 °C within its thermodynamic uncertainty of 0.12 °C (k= 2). © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627093

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Results of experimental determinations of thermodynamic temperatures using Fourier transform spectroscopy of blackbody radiation sources are presented. These results are augmented by and compared with theoretical simulations of blackbody spectra in order to assess the feasibility and accuracy of the method. Much of the information on thermodynamic temperature contained in such spectral sets is redundant, and we present a method (based on the original suggestion by Gebbie and recent work done at NRC) to exploit this redundancy in a straightforward way to obtain thermodynamic temperatures for each of the spectral sources. Here, we briefly describe the experimental apparatus, the analysis of the most recent experimental results and a comparison with our simulations. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627094

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The NIST Primary Acoustic Thermometer will measure the difference between the International Temperature Scale of 1990 and the Kelvin Thermodynamic Scale throughout the range 273 K to 800 K with uncertainties of only a few millikelvins. The acoustic thermometer determines the frequencies of the acoustic resonances of pure argon gas contained within a spherical cavity with uncertainties approaching one part in 106. To achieve this small uncertainty at these elevated temperatures we developed new acoustic transducers and new techniques for the maintenance of gas purity and for temperature control. The new electro‐acoustic transducers are based on the capacitance between a flexible silicon wafer and a rigid backing plate. Without the damping usually provided by polymers, mechanical vibrations caused unstable, spurious acoustic signals. We describe our techniques for suppression of these vibrations. Our acoustic thermometer allows the argon to be continuously flushed through the resonator, thereby preventing the build up of hydrogen that evolves from the stainless‐steel resonator. We describe how the argon pressure is stabilized while flushing. The argon exiting from the resonator is analyzed with a customized gas chromatograph. Because the acoustic resonator was so large—it has an outer diameter of 20 cm—a sophisticated furnace, based on surrounding the resonator with three concentric aluminum shells, was designed to maintain thermal uniformity and stability of the resonator at a level of 1 mK. We describe the design, modeling, and operational characteristics of the furnace. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627095

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The NIST Acoustic Thermometer determines the thermodynamic temperature by measuring the speed of sound of argon in a spherical cavity. We obtained the thermodynamic temperature of three fixed points on the International Temperature Scale of 1990: the melting point of gallium [T(Ga) = 302.9146 K] and the freezing points of indium [T(In) = 429.7485 K] and tin [T(Sn) = 505.078 K]. The deviations of thermodynamic temperature from the ITS‐90 defined temperatures areT−T90= (4.7 ± 0.6) mK atT(Ga) ,T−T90= (8.8 ± 1.5) mK atT(In) , andT−T90= (10.7 ± 3.0) mK atT(Sn) , where the uncertainties are for a coverage factor ofk= 1. Our results atT(In) andT(Sn) reduce the uncertainty ofT−T90by a factor of two in this range. BothT−T90atT(Ga) and the measured thermal expansion of the resonator between the triple point of water andT(Ga) are in excellent agreement with the 1992 determination at NIST. The dominant uncertainties in the present data come from frequency‐dependent and time‐dependent crosstalk between the electroacoustic transducers. We plan to reduce these uncertainties and extend this work to 800 K. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627096

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Johnson Noise Thermometry (JNT) involves the measurement of the statistical variance of a fluctuating voltage across a resistor in thermal equilibrium. Modern digital techniques make it now possible to perform many functions required for JNT in highly efficient and predictable ways. We describe the operational characteristics of a prototype JNT system which uses digital signal processing for filtering, real‐time spectral cross‐correlation for noise power measurement, and a digitally synthesized Quantized Voltage Noise Source (QVNS) as an AC voltage reference. The QVNS emulates noise with a constant spectral density that is stable, programmable, and calculable in terms of known parameters using digital synthesis techniques. Changes in analog gain are accounted for by alternating the inputs between the Johnson noise sensor and the QVNS. The Johnson noise power at a known temperature is first balanced with a synthesized noise power from the QVNS. The process is then repeated by balancing the noise power from the same resistor at an unknown temperature. When the two noise power ratios are combined, a thermodynamic temperature is derived using the ratio of the two QVNS spectral densities. We present preliminary results where the ratio between the gallium triple point and the water triple point is used to demonstrate the accuracy of the measurement system with a standard uncertainty of 0.04 &percent;. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627097

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The kinetic theory of rarefied gases is used to show that there is a difference between the kinetic temperature and the thermodynamic one. The former represents the mean kinetic energy of the molecules while the latter is the one measured by a contact thermometer. The argument is based upon a recent paper [1] by Mu¨ller and Ruggeri. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627098

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The construction of the temperature scale PTB‐96 below 15 mK relies on platinum NMR thermometry. The quality of the Curie law for pure platinum metal and the limitations set by magnetic impurities are discussed. The solution found to overcome the resulting difficulties is described, and an uncertainty budget is drawn up. Measurements with different instrumentation supporting the NMR temperature scale are also presented. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627099

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Estimates of the non‐uniqueness of the ITS‐90 are reported based on comparisons of capsule‐style standard platinum resistance thermometers at more than eighty temperatures between 13.8033 K and 273.16 K. Using the measurements reported here, as well as those of Ward and Compton and Head, we conclude that the non‐uniqueness takes on its largest value (± 0.4 mK) in the range from 83.8058 K to 234.3156 K. This result may have been anticipated due to the fact that the argon and mercury fixed points are separated in temperature by more than 150 K, with no intermediate calibration points. Discussions concerning the details of the temperature scale that will eventually replace the ITS‐90 must consider this fact if the non‐uniqueness is to be minimized. At the present time, however, there are no candidate fixed points within this temperature range that are realizable to the required level of accuracy for inclusion into a revised International Temperature Scale. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1627100

出版商:AIP    

年代:1903

数据来源: AIP