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One-port Electronic Detection Strategies for Improving Sensitivity in Piezoelectric Resonant Sensor Measurements

Lookup NU author(s): Dr Zhongxu Hu, Dr John Hedley, Dr Neil Keegan, Julia Spoors, Dr Barry Gallacher, Emeritus Professor Calum McNeil

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

This paper describes a one-port mechanical resonance detection scheme utilized on a piezoelectric thin film driven silicon circular diaphragm resonator and discusses the limitations to such an approach in degenerate mode mass detection sensors. The sensor utilizes degenerated vibration modes of a radial symmetrical microstructure thereby providing both a sense and reference mode allowing for minimization of environmental effects on performance. The circular diaphragm resonator was fabricated with thickness of 4.5 µm and diameter of 140 µm. A PZT thin film of 0.75 µm was patterned on the top surface for the purposes of excitation and vibration sensing. The device showed a resonant frequency of 5.8 MHz for the (1, 1) mode. An electronic interface circuit was designed to cancel out the large static and parasitic capacitance allowing for electrical detection of the mechanical vibration thereby enabling the frequency split between the sense and reference mode to be measured accurately. The extracted motional current, proportional to the vibration velocity, was fed back to the drive to effectively increase the Q factor, and therefore device sensitivity, by more than a factor of 8. A software phase locked loop was implemented to automatically track the resonant frequencies to allow for faster and accurate resonance detection. Results showed that by utilizing the absolute mode frequencies as an indication of sensor temperature, the variation in sensor temperature due to the heating from the drive electronics was accounted for and led to an ultimate measurement sensitivity of 2.3 Hz.


Publication metadata

Author(s): Hu Z, Hedley J, Keegan N, Spoors J, Gallacher B, McNeil C

Publication type: Article

Publication status: Published

Journal: Sensors

Year: 2016

Volume: 16

Issue: 11

Pages: 1781

Online publication date: 25/10/2016

Acceptance date: 20/10/2016

Date deposited: 20/10/2016

ISSN (electronic): 1424-8220

Publisher: MDPI

URL: http://dx.doi.org/10.3390/s16111781

DOI: 10.3390/s16111781

Data Source Location: http://dx.doi.org/10.17634/082208-1


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