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High resolution electric field imaging using ultra-low capacitance probes

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thesis
posted on 2024-01-08, 11:39 authored by Philip Watson

Imaging of material properties by direct measurement of electric field allows the non-contact determination of a number of important properties. The development of ultra-low capacitance probes for high spatial resolution measurements, based on the Electric Potential Sensor, forms the bulk of the work in this thesis. This sensor's unique and low capacitance design enables the use of smaller sense electrodes, down to 6 μm, while still maintaining a relatively wide signal bandwidth. The imaging techniques presented have significant advantages over other methods where mesoscopic spatial resolution is required. Three distinct measurement modes are explored which variously allow the imaging of surface topography, dielectric constant, static charge density and electrical conductivity.

The Electric Potential Sensor is a generic sensing technology developed at the University of Sussex. Details of various sensor designs and the applications of the sensors to the imaging of electric potentials has been published previously and demonstrated for the non-destructive testing of composites and the imaging of signals in digital integrated circuits. These previous investigations have been limited primarily by shortcomings in the probe design, particularly the sensitivity, spatial resolution, stability, and versatility.

An ultra-low capacitance probe is designed using discrete transistors. The characterisation and application of this sensor to high resolution imaging is described. Results, using this design, are presented for the first microscopic charge imaging system to provide time dependent charge density information. In addition, the use of both phase and amplitude for information obtained from a.c. signals is demonstrated. The wider application of this sensor to other measurements is discussed, including the remote electrocardiograph and the contact electromyogram. In each case the benefits of increased dynamic range and reduced input capacitance are demonstrated. By investigating the implementation of the sensors using discrete transistors, the additional possibility of producing a CMOS integrated sensor is explored.

History

File Version

  • Published version

Pages

207

Department affiliated with

  • Engineering and Design Theses

Qualification level

  • doctoral

Qualification name

  • phd

Language

  • eng

Institution

University of Sussex

Full text available

  • Yes

Supervisor

Prof Robert J Prance and Dr Christopher J Harland

Legacy Posted Date

2012-09-26

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