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A MEMS Dual Vertical Electrometer and Electric Field-Mill George C Air Force Institute of Technology AFIT Scholar Theses and Dissertations Student Graduate Works 3-22-2019 A MEMS Dual Vertical Electrometer and Electric Field-Mill George C. Underwood Follow this and additional works at: https://scholar.afit.edu/etd Part of the Electro-Mechanical Systems Commons Recommended Citation Underwood, George C., "A MEMS Dual Vertical Electrometer and Electric Field-Mill" (2019). Theses and Dissertations. 2288. https://scholar.afit.edu/etd/2288 This Thesis is brought to you for free and open access by the Student Graduate Works at AFIT Scholar. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of AFIT Scholar. For more information, please contact [email protected]. A MEMS DUAL VERTICAL ELECTROMETER AND ELECTRIC FIELD-MILL THESIS George C. Underwood, Second Lieutenant, USAF AFIT-ENG-MS-19-M-063 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio DISTRIBUTION STATEMENT A. APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. The views expressed in this thesis are those of the author and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the United States Government. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. AFIT-ENG-MS-19-M-063 A MEMS DUAL VERTICAL ELECTROMETER AND ELECTRIC FIELD-MILL THESIS Presented to the Faculty Department of Electrical and Computer Engineering Graduate School of Engineering and Management Air Force Institute of Technology Air University Air Education and Training Command In Partial Fulfillment of the Requirements for the Degree of Master of Science George C. Underwood, B.S.E.E. Second Lieutenant, USAF March 2019 DISTRIBUTION STATEMENT A. APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. AFIT-ENG-MS-19-M-063 A MEMS DUAL VERTICAL ELECTROMETER AND ELECTRIC FIELD-MILL THESIS George C. Underwood, B.S.E.E. Second Lieutenant, USAF Committee Membership: Maj. Tod V. Laurvick, PhD Chair Dr. Hengky Chandrahalim, PhD Member Dr. Frank Kenneth Hopkins, PhD Member AFIT-ENG-MS-19-M-063 Abstract Presented is the first iteration of a Microelectromechanical System (MEMS) dual vertical electrometer and electric field-mill (EFM). The device uses a resonating structure as a variable capacitor that converts the presence of a charge or field into an electric signal. Previous MEMS electrometers are lateral electrometers with laterally spaced electrodes that resonate tangentially with respect to each other. Vertical electrometers, as the name suggests, have vertically spaced electrodes that resonate transversely with respect to each other. The non-tangential movement reduces damping in the system. Both types demonstrate comparable performance, but the vertical electrometer does so at a fraction of the size. In addition, vertical electrometers can efficiently operate as an electric field sensor. The electric field sensor simulations did not compare as well to other MEMS electric field sensors. However, the dual nature of this device makes it appealing. These devices can be used in missiles and satellites to monitor charge buildup in electronic components and the atmosphere [11]. Future iterations can improve these devices and give way to inexpensive, high-resolution electrostatic charge and field sensors. iv Acknowledgments I would first like to thank my advisor, Maj Laurvick for trusting me in this endeavor, for never having doubts even when I had many. I would also like to thank Dr. Chandrahalim for his constant support and vast knowledge in this subject, and Dr. Frank (Ken) Hopkins for his intellect and willingness to be on the committee. I also thank everyone in the MEMS Group for the fraternity that made the past year and a half so enjoyable. I appreciate Dr. David Torres for his friendship and assistance at AFRL. I would next like to thank my family. Mom and Dad, thank you for everything; you inspire me to challenge myself and not to live life with an excuse. I sincerely thank Blaine Underwood, my biggest competition and role model. You’re the iron to my iron, we sharpen each other. Of course, I thank my beautiful Fiancée for being a beacon of joy in difficult times. Finally, I thank God, the guidance of the Holy Spirit, the immaculate heart of Mary, the protection of St. Joseph, and all the angels and saints for assisting me day-to-day. George C. Underwood v Table of Contents Page Abstract .............................................................................................................................. iv Table of Contents ............................................................................................................... vi List of Figures .................................................................................................................... ix List of Tables ................................................................................................................... xiii I. Introduction ..................................................................................................................1 II. Literature Review .........................................................................................................4 2.1 Chapter Overview ...............................................................................................4 2.2 Variable Capacitor Based MEMS Electrostatic Charge and Field Sensors ........4 2.3 Noise Analysis.....................................................................................................5 2.3.1 Thermal Noise ..................................................................................................7 2.3.2 Leakage ............................................................................................................8 2.3.3 Flicker Noise ..................................................................................................10 2.3.4 KT/C Noise ....................................................................................................11 2.3.5 Brownian Noise .............................................................................................12 2.3.6 Noise Mixing .................................................................................................13 2.3.7 Feedthrough ...................................................................................................14 2.4 Riehl’s Electrometer ..........................................................................................18 2.5 Riehl’s E-field Sensor .......................................................................................20 2.6 Mechanics..........................................................................................................21 2.6.1 Actuation ........................................................................................................22 2.6.2 Suspension .....................................................................................................26 2.6.3 Damping .........................................................................................................27 vi 2.7 Conclusion .........................................................................................................28 III. Theory and Methodology ...........................................................................................32 3.1 Chapter Overview .............................................................................................32 3.2 Fabrication .........................................................................................................33 3.3 Electromechanical Characterization ..................................................................35 3.4 Electrometer Sensitivity Analysis .....................................................................38 3.5 Electrometer Noise Analysis .............................................................................41 3.6 Experimental Setup of Electrometer .................................................................43 3.7 Electric Field-Mill Sensitivity Analysis ............................................................45 3.8 Electrostatic Field-Mill Noise Analysis ............................................................47 3.9 Experimental setup of EFM ..............................................................................49 3.10 Summary ........................................................................................................50 IV. Results ........................................................................................................................51 4.1 Chapter Overview .............................................................................................51 4.2 Simulation Results.............................................................................................51 4.2.1 Mechanical Simulations .................................................................................51 4.2.2 Electrometer Simulations ...............................................................................53 4.2.3 E-Field Simulations .......................................................................................54 4.3 Electromechanical Results ................................................................................57 4.3.1 Mechanical Measurements.............................................................................58 4.4 Electrometer Results .........................................................................................62
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