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Whispering Gallery Mode Thermometry

Department of Electronics and Telecommunications, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy
College of Electrical Engineering and Control Science, Nanjing Tech University, Nanjing 211816, China
Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, Torino 10135, Italy
Authors to whom correspondence should be addressed.
Academic Editor: Stephane Evoy
Sensors 2016, 16(11), 1814;
Received: 1 September 2016 / Revised: 18 October 2016 / Accepted: 25 October 2016 / Published: 29 October 2016
(This article belongs to the Special Issue Resonator Sensors)
PDF [8668 KB, uploaded 1 November 2016]


This paper presents a state-of-the-art whispering gallery mode (WGM) thermometer system, which could replace platinum resistance thermometers currently used in many industrial applications, thus overcoming some of their well-known limitations and their potential for providing lower measurement uncertainty. The temperature-sensing element is a sapphire-crystal-based whispering gallery mode resonator with the main resonant modes between 10 GHz and 20 GHz. In particular, it was found that the WGM around 13.6 GHz maximizes measurement performance, affording sub-millikelvin resolution and temperature stability of better than 1 mK at 0 °C. The thermometer system was made portable and low-cost by developing an ad hoc interrogation system (hardware and software) able to achieve an accuracy in the order of a few parts in 109 in the determination of resonance frequencies. Herein we report the experimental assessment of the measurement stability, repeatability and resolution, and the calibration of the thermometer in the temperature range from −74 °C to 85 °C. The combined standard uncertainty for a single temperature calibration point is found to be within 5 mK (i.e., comparable with state-of-the-art for industrial thermometry), and is mainly due to the employed calibration setup. The uncertainty contribution of the WGM thermometer alone is within a millikelvin. View Full-Text
Keywords: whispering gallery mode resonators; temperature sensors; high-accuracy thermometry; microwave resonance; sapphire-based dielectric thermometry whispering gallery mode resonators; temperature sensors; high-accuracy thermometry; microwave resonance; sapphire-based dielectric thermometry

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Corbellini, S.; Ramella, C.; Yu, L.; Pirola, M.; Fernicola, V. Whispering Gallery Mode Thermometry. Sensors 2016, 16, 1814.

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