Systematic Errors in a High-Accuracy Johnson Noise Thermometer

The design of a cross-correlation noise thermometer based on a very-low-noise preamplifier and a high-speed, high-accuracy analog-to-digital converter is described. Error estimations indicate that the thermometer will have a basic accuracy better than 10 mK. Further self-check procedures are outlined that will reduce the systematic errors to approximately ±2 mK. The measurement time required to achieve a statistical uncertainty of ±3 mK is 2.5 days. A thermometer of the design suggested is under construction at the Physics and Engineering Laboratory of the DSIR, for operation between 0 °C and 200 °C.