A Johnson noise thermometer with traceability to electrical standards

The paper presents an absolute Johnson noise thermometer (JNT), an instrument to measure the thermodynamic temperature of a sensing resistor, with traceability to voltage, resistance and frequency quantities. The temperature is measured in energy units, and can be converted to SI units (kelvin) with the accepted value of the Boltzmann constant kB; or, conversely, it can be employed to perform measurements at the triple point of water and obtain a determination of kB. The thermometer is composed of a correlation spectrum analyzer and a calibrator. The calibrator generates a pseudorandom noise (at a level suitable for traceability to an ac voltage standard) by digital synthesis, scaled in amplitude by a chain of electromagnetic voltage dividers and cyclically injected in series with the Johnson noise. First JNT measurements at room temperature are compatible with those of a standard platinum resistance thermometer within the estimated combined uncertainty of 60 µK K −1 of both instruments. A path towards future improvements of JNT accuracy is also sketched.

[1]  Luca Callegaro,et al.  Direct-reading absolute calibration of ac voltage ratio standards , 2002, Conference Digest Conference on Precision Electromagnetic Measurements.

[2]  John M. Martinis,et al.  Johnson noise thermometry measurements using a quantized voltage noise source for calibration , 2003, IEEE Trans. Instrum. Meas..

[3]  S. P. Benz,et al.  Constraints on a synthetic-noise source for Johnson noise thermometry , 2008 .

[4]  Dean C. Ripple,et al.  Acoustic Thermometry Results from 271 to 552 K , 2007 .

[5]  Luigi Iacomini,et al.  A liquid bath for accurate temperature measurements , 2007 .

[6]  Joachim Fischer,et al.  Determination of the Boltzmann constant—status and prospects , 2006 .

[7]  David White,et al.  Preamplifier limitations on the accuracy of Johnson noise thermometers , 2000 .

[8]  D. A. Wilbur.  Thermal Agitation of Electricity in Conductors. , 1932 .

[9]  B. Taylor,et al.  CODATA recommended values of the fundamental physical constants: 2006 | NIST , 2007, 0801.0028.

[10]  P. Simonson,et al.  Loading errors in low voltage AC measurements , 1996, Proceedings of 20th Biennial Conference on Precision Electromagnetic Measurements.

[11]  Sae Woo Nam,et al.  Improvements in the NIST Johnson noise thermometry system , 2008, 2008 Conference on Precision Electromagnetic Measurements Digest.

[12]  Weston L. Tew,et al.  Measurement time and statistics for a noise thermometer with a synthetic-noise reference , 2008 .

[13]  B. N. Taylor,et al.  The 1986 CODATA Recommended Values Of the Fundamental Physical Constants , 1987, Journal of Research of the National Bureau of Standards.

[14]  J. J. Hill,et al.  Two-stage inductive voltage dividers , 1968 .

[15]  L. Storm.  Precision Measurements of the Boltzmann Constant , 1986 .

[16]  A Actis,et al.  The status of Johnson noise thermometry , 1996 .

[17]  A. Merlone,et al.  Acoustic measurements of the thermodynamic temperature between the triple point of mercury and 380 K , 2004 .

[19]  J. Johnson.  Thermal Agitation of Electricity in Conductors , 1928 .

[20]  Bruno Trinchera,et al.  Reconfigurable Unit for Precise RMS Measurements , 2009, IEEE Transactions on Instrumentation and Measurement.