Callaghan Innovation Research Papers

Back to Research Papers

TitleMeasurement time and statistics for a noise thermometer with a synthetic-noise reference
Publication TypeJournal Article
Year of Publication2008
AuthorsWhite, D.R., Benz S.P., Labenski J.R., Nam S.W., Qu J.F., Rogalla H., and Tew W.L.
Pagination395 - 405
Date Published2008
ISSN00261394 (ISSN)
KeywordsCorrelation methods, Correlators, Noise thermometers, Pseudo-random noise, Random errors, Random processes, Reference signal, Regression analysis, Statistical methods, Telecommunication systems, Temperature measurement, Temperature measuring instruments, Temperature sensors, Thermometers, Uncertainty analysis
AbstractThis paper describes methods for reducing the statistical uncertainty in measurements made by noise thermometers using digital cross-correlators and, in particular, for thermometers using pseudo-random noise for the reference signal. First, a discrete-frequency expression for the correlation bandwidth for conventional noise thermometers is derived. It is shown how an alternative frequency-domain computation can be used to eliminate the spectral response of the correlator and increase the correlation bandwidth. The corresponding expressions for the uncertainty in the measurement of pseudo-random noise in the presence of uncorrelated thermal noise are then derived. The measurement uncertainty in this case is less than that for true thermal-noise measurements. For pseudo-random sources generating a frequency comb, an additional small reduction in uncertainty is possible, but at the cost of increasing the thermometer's sensitivity to non-linearity errors. A procedure is described for allocating integration times to further reduce the total uncertainty in temperature measurements. Finally, an important systematic error arising from the calculation of ratios of statistical variables is described. © 2008 BIPM and IOP Publishing Ltd.

Back to top