Since Johnson's experimental observations of thermal noise in 1927, and Nyquist's explanation of the phenomenon shortly afterwards in 1928, thermal noise has attracted interest as a means of measuring temperature. The independence of the thermal noise from the material nature of the sensor makes it particularly attractive for metrological applications. However, the noise signals are extremely small and some ingenuity is required to make accurate measurements. This paper reviews the foundations of Johnson noise thermometry and the various techniques that have been employed to measure temperature via Johnson noise. Emphasis is placed on key developments in noise thermometers for metrological applications. The review includes the current activities of teams involved in noise thermometry research.

A noise thermometer has been developed at IMGC and has been used to realize the Thermodynamic Scale (TS). Differences between TS, as realized at IMGC, and the IPTS-68 were determined in the range 630-962OC and the results are presented.The discussion of results primarily deals with the factors introducing measurement uncertainties and with the comparison of noise thermometer results with those of recent radiation thermometry and gas thermometry experiments.Data fitting provides the TS versus IPTS-68 differences as a continuous function of the Celsius temperature in the range 630-1064°C. For this, data from monochromatic pyrometry experiments are taken into account in order to cover the range from the freezing point of silver to the freezing point of gold.

No abstract

No abstract