Absolute high-temperature Johnson noise thermometry

Abstract
A switching noise thermometer incorporating a series-resonant filter between the sensor and reference resistors and the amplifier stages is described. The first-order dependence of the temperature measurement on the magnitudes of the sensor and reference resistances and also on the magnitude of any stray capacitance is thereby removed. The DC voltage developed across a shot-noise diode load (the reference resistor) gives a direct measurement of the difference between the absolute temperatures of the sensor and reference resistors. The configuration enables noise signal bandwidths of 0.5 MHz to be used, allowing temperatures to be measured with a statistical uncertainty of 0.2% with a 1 s measurement time. FETS are incorporated at the input of the system in place of the conventional electromechanical switches.

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