About 25 years ago, I first visited the Instrumentation Labs at Oak Ridge National Laboratories (ONRL) at the invitation of the late Bob Shepard. Bob was a pioneer in many areas of temperature measurement and at that time was the Chairman of ASTM Committee E20 on Temperature. He was also head of the lab at ORNL.

He introduced me to Johnson Noise Temperature (JNT) measurement and showed me a prototype device that they had developed at Oak Ridge to implement the method as an possible alternate means to verify the calibration in situ of thermocouples in a nuclear reactor environment.

While the method was very complex, Bob was convinced it would eventually become commercially viable, if for no other reason than it was a fundamental technology related to the Absolute Thermodynamic Temperature Scale (Kelvin Scale) and required no calibration.

Work has continued to this day at ORNL and elsewhere. More recently, the staff at the National Institute of Standards & Technology (NIST) Thermometry Group have been producing some remarkable results, prototype devices and a raft of technical papers on the subject.

First a description about this unique temperature measurement method that has been studied for more than 30 years.

The description below is from the NIST Thermometry Group Website and is almost an exact quote:

Johnson noise thermometry (JNT) utilizes the fundamental properties of thermal fluctuations in conductors. Because the technique is a primary method, as opposed to a secondary or artifact method, the sensor response does not require calibration.

An innovative JNT method now being developed at NIST links the measured thermal voltage directly to the as-maintained electrical units via the AC Josephson Voltage Standard. The work is part of a NIST competence initiative formed by a collaboration between the Process Measurements Division (Gaithersburg MD) and the Quantum Electrical Metrology Division (Boulder CO).

The project also has an international collaborator, the MSL/IRL in New Zealand.

The NIST JNT competence project has already demonstrated that the new methodology can achieve accuracies over the range between 273 K and 303 K sufficient for many applications. In the absolute mode, the current agreement between a Quantized Voltage Noise Source (QVNS).-derived noise temperatures and the ITS-90/SI assignments for the Gallium Triple Point (Ga TP) and the Triple Point of Water (H2O TP) fixed points is 150 mK/K to 300 mK/K.

Next, a list of Technical papers and presentations about the NIST work that can be found on the NIST Boulder CO website (Also almost an exact quote):

NIST Reference papers on Johnson Noise Thermometry:

Johnson Noise Thermometry Papers

S. Nam, S. Benz, P. Dresselhaus, C. Burroughs, W. L. Tew, D. R. White, J. M. Martinis, “Johnson Noise Thermometry using a Quantum Voltage Noise Source for Calibration,” IEEE Transactions on Instrumentation and Measurement, Vol. 54, No. 2, (April 2005), to be published.
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S. W. Nam , S. P. Benz, J. M. Martinis, P.D. Dresselhaus, W. L. Tew, and D. R. White, “A ratiometric method for Johnson noise thermometry using a quantized voltage noise source”, in Temperature: Its Measurement and Control In Science and Industry, Vol. 7, Part 1, pp. 37-42, Edited by Dean C. Ripple, Proceedings of The Eighth International Temperature Symposium, 21-24 October 2002, Chicago, Illinois, USA (AIP Conference Proceedings Vol. 684: Melville, New York 2003).
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S. Nam, S. Benz, P.D. Dresselhaus, and J. Martinis, “Johnson noise thermometry measurements using a quantized voltage noise source for calibration”, IEEE Trans. Instrum. Meas., Vol. 52, No. 2, pp. 550-554 (April 2003).
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S.P. Benz, P.D. Dresselhaus, and J. Martinis, “An ac Josephson source for Johnson noise thermometry”, IEEE Transactions on Instrumentation and Measurement, Vol. 52, No. 2, pp. 545-549 (April 2003).
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S. P. Benz, J. M. Martinis, S. W. Nam, W. L. Tew, and D. R. White, “A new approach to Johnson noise thermometry using a Josephson quantized voltage source for calibration”, in Proceedings of TEMPMEKO 2001, the 8th International Symposium on Temperature and Thermal Measurements in Industry and Science, B. Fellmuth, J. Seidel, and G. Scholz, Eds., Berlin: VDE Verlag, April 2002, pp. 37-44.
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