Johnson Noise Thermometry is an electronic approach to measuring temperature. For several years, NIST has been developing a switching-correlator-type Johnson-noise thermometer that uses a quantized voltage noise source as an accurate voltage reference. When this method is used to measure resistors at the triple-point of water, the system creates a direct electronic method for determining the ratio of the Boltzmann constant k to the Planck constant h. In 2010, NIST optimized the JNT system for use with 100 ohm sense resistors and produced a determination for k with a relative standard uncertainty of 12x10^-6. In order to further validate and improve the measurement method, we modified the system to operate with a 200 ohm resistor source instead of the 100 ohm source. In this paper, we summarize the technical challenges and achievements to date and project what is achievable in the near future.
Proceedings Title: Temperature: Its Measurement and Control in Science and Industry, Vol. 8
Conference Dates: March 19-23, 2012
Conference Location: Anaheim, CA
Conference Title: 9th International Temperature Symposium (ITS9)
Pub Type: Conferences
Johnson noise thermometry, Boltzmann equation, Correlation, Digital-analog conversion, Josephson arrays, Measurement units, Noise Measurement, Quantization, Signal synthesis, Standards, Temperature.