23rd IMEKO TC 4 International Symposium and the 5th Chinese Conference on Electromagnetic Metrology Technical (IMEKO TC4 2019)

225 / 2019-06-26 12:37:17

Comparsion of different kinds of frequency scanning methods used at low temperatures

SPRIGT, microwave resonator, frequency scanning, quasi-spherical

Plenary track > Time and Frequency Measurements

A novel single pressure refractive index gas thermometry (SPRIGT) has been collaboratively developed by the TIPC-CAS in China and the LNE-Cnam in France [1]. In the SPRIGT, microwave resonance frequencies are used to determine the refractive index of a working gas in a quasi-spherical resonator at a single pressure and temperature. Then an unknown temperature can be determined by comparing the refractive index with that at a reference temperature. Usually, the resonance frequencies were obtained by fitting the S21 scattering parameters with respect to the scanning frequencies, which are generated by a network analyzer using a frequency list generating routine. To realize high accuracy measurement in frequency at low temperatures, three kinds of frequency list generating method (scanning method), namely frequency uniform method, phase angle uniform method and their hybridization method (mixed method), have been investigated. The results show the phase angle uniform and mixture method is easier to realize high accuracy measurement than frequency uniform method at low temperature. Besides, long-time stability in frequency were also studied in this work, the shows that the phase angle uniform and mixture method have a same level stability, thus they can be used in the SPRIGT.