Low-Cost Instrument for Whispering Gallery Mode Thermometry up to 19 GHz

partially_open5In this paper, a portable low-cost system for the accurate measurement of complex resonance frequencies up to 19 GHz for whispering gallery mode thermometry is presented and validated. The instrument performs vectorial transmission measurements for the determination of resonance frequencies with accuracy in the order of a few parts in in 109 over two different RF/microwave bands: 1) 800 MHz-7 GHz and 2) 13-19 GHz. The former band is suitable for quasi-spherical resonator (QSR)-based experiments, currently of great interest in different metrological applications, while the latter is expressly supported for whispering gallery thermometry. The capability of the instrument to meet the performance required for whispering gallery thermometry is first verified using an extremely stable setup based on a QSR. Afterward, the calibration of the whispering gallery thermometer composed of the developed instrument and an existing resonator is performed. The obtained results prove the suitability of the instrument to replace vector network analyzers in accurate resonance-based experiments and also its capability to enable the use of whispering gallery thermometers as transfer standards in the industrial field.partially_openCORBELLINI S., RAMELLA C., PIROLA M., FERNICOLA V., CAPPELLA A.Corbellini, S.; Ramella, C.; Pirola, M.; Fernicola, V.; Cappella, A

Whispering gallery mode thermometry

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

Low-Cost Instrument for Whispering Gallery Mode Thermometry up to 19 GHz

In this paper, a portable low-cost system for the accurate measurement of complex resonance frequencies up to 19 GHz for whispering gallery mode thermometry is presented and validated. The instrument performs vectorial transmission measurements for the determination of resonance frequencies with accuracy in the order of a few parts in 10^9 over two different RF/microwave bands: 1) 800 MHz–7 GHz and 2) 13–19 GHz. The former band is suitable for quasi-spherical resonator (QSR)-based experiments, currently of great interest in different metrological applications, while the latter is expressly supported for whispering gallery thermometry. The capability of the instrument to meet the performance required for whispering gallery thermometry is first verified using an extremely stable setup based on a QSR. Afterward, the calibration of the whispering gallery thermometer composed of the developed instrument and an existing resonator is performed. The obtained results prove the suitability of the instrument to replace vector network analyzers in accurate resonance-based experiments and also its capability to enable the use of whispering gallery thermometers as transfer standards in the industrial field

Applications of Microwave Resonators to Thermal Metrology

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