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| Temperature Measurements and Standards |
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| Objective: |
Realize and disseminate the International Temperature Scale of 1990 (ITS-90) to U.S. industry and government agencies. Establish equivalence of U.S. National standards with U.S. trading partners through comparison activities with the CIPM and regional metrology organizations. Develop new approaches to temperature measurements useful in advanced industrial processes. |
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| Description: |
| NIST has been the first NMI to fully realize the ITS-90 for contact thermometry in the range of 0.65 K to 1235 K. To effectively disseminate the ITS-90, measurement services are provided to a broad range of users. Research efforts focus on advancing the state-of-the-art in thermometry by developing methods and devices that:
- Assist user groups in the assessment and enhancement of the accuracy of their temperature measurements, Promote effective measurement methods through participation in standards development organizations,
- Enable industrial users to attain traceability to the ITS-90 in demanding industrial environments, such as in-situ calibration of radiometers in Rapid Thermal Processing (RTP) tools used in semiconductor manufacturing,
- Use high accuracy methods for the determination of thermodynamic temperature to investigate deviations of the ITS-90 from thermodynamic values as a basis for improvements to future temperature scales, and
- Develop new measurement methods and approaches for thermometry to improve temperature measurements and standards.
Continuing assessment of measurement needs is addressed through the hosting of workshops and conferences on thermometry techniques, and formal and informal interactions with industrial users. Quality principles are used as a means to maximize the value of NIST calibration services to our customers. NIST also seeks to enhance international trade through the mutual recognition of national measurement standards and is engaged in comparison efforts with other NMIs to establish levels of equivalence in the realization of the ITS-90. |
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| Area(s) of Application: |
- Industrial and Analytical Instruments
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| Accomplishments: |
- Dissemination of the ITS-90 : Instrument calibration services are offered over the full contact thermometry range
- NIST Quality Supporting Measurement Services : Implemented NIST Quality System supporting NIST thermometry calibration services.
- Primary Acoustic Thermometry : NIST scientists are using a state-of-the-art acoustic thermometer to make high accuracy determinations of thermodynamic temperature at the ITS-90 defining points of the melting point of gallium (302 K, 29.75 ºC), and the freezing points of indium (429.7485 K, 156.5985 ºC) and tin indium (505.078 K, 231.928 ºC). These data have resolved discrepancies between the ITS-90 and thermodynamic temperature and will be used in the development of future temperature scales expected to be formulated in the next decade.
- Johnson Noise Thermometry : JNT is a primary thermometry technique with good potential for high accuracy in demanding application environments and as an absolute, high-temperature contact method for thermodynamic temperature determinations. NIST scientists have demonstrated a new approach to JNT that utilizes a Josephson junction-based quantum voltage noise standard (QVNS) as an intrinsically calculable noise voltage source. The QVNS substantially increases achievable accuracy of JNT for high temperature, harsh environment applications. Temperature measurement uncertainties of 250 µK/K in the absolute mode and 100 µK/K in the relative mode have been demonstrated.
- Standards for Rapid Thermal Processing (RTP) of Semiconductors : NIST has developed silicon wafer-based artifacts for RTP tools suitable for the accurate calibration of the radiometric devices, lightpipe radiation thermometers (LPRTs), used for tool control. Measurement uncertainty of ± 2 ºC from 600 ºC to 900 ºC has been achieved using a NIST-patented thin-film/wire thermocouple design.
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| Future Plans: |
- JNT : Develop high temperature probes and reduce the measurement uncertainty of the method.
- RTP : Develop and characterize resistance sensor technology for in situ calibration wafers in the range 300 °C to 650 °C having measurement uncertainties below 0.05 °C.
- Future Temperature Scales : Extend the measurement range in primary acoustic thermometry to ~800 K (527 °C).
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| Recent Publications: |
- Nam , S.W., Benz, S.P., Martinis, J.M., Dresselhaus, P., Tew, W.L., and White, D.R., “A Ratiometric Method for Johnson Noise Thermometry Using a Quantized Voltage Noise Source,” Temperature: Its Measurement and Control in Science and Industry , Vol. 7.
- Ripple, D.C., Garrity, K.M., and Meyer, C.W., “A Four-Zone Furnace for Realization of Silver and Gold Freezing Points,” Temperature: Its Measurement and Control in Science and Industry , Vol. 7.
- Vaughn, C.D., Gartenhaus, J., and Strouse, G.F., “NIST Calibration Uncertainties of Thermistor Thermometers over the Range from -50 ° C to 90 ° ,” Proc. 2005 NCSLI Intl. Workshop and Symposium
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| Relevant Links: |
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| Principal Investigator: Dean Ripple |
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