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Sensors 2016, 16(11), 1781;

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

School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
Author to whom correspondence should be addressed.
Academic Editor: Stephane Evoy
Received: 12 July 2016 / Revised: 3 October 2016 / Accepted: 20 October 2016 / Published: 25 October 2016
(This article belongs to the Section Physical Sensors)
Full-Text   |   PDF [5071 KB, uploaded 25 October 2016]   |  


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. View Full-Text
Keywords: microsensors; piezoelectric resonators; self-sensing; frequency tracking microsensors; piezoelectric resonators; self-sensing; frequency tracking

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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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Hu, Z.; Hedley, J.; Keegan, N.; Spoors, J.; Gallacher, B.; McNeil, C. One-Port Electronic Detection Strategies for Improving Sensitivity in Piezoelectric Resonant Sensor Measurements. Sensors 2016, 16, 1781.

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