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International Society for Industrial Process Tomography

2nd World Congress on Industrial Process Tomography

Key Issues in the Design of a Capacitance Transducer for Tomography


D Georgakopoulos and W Q Yang


Dept. of Electrical Engineering and Electronics, UMIST, PO Box 88 Sackville Street, Manchester M60 1QD, UK dimitrios.georgakopoulos@stud.umist.ac.uk, w.yang@umist.ac.uk


ABSTRACT


The real and imaginary parts of the complex permittivity are used to characterise dielectric materials, and some industrial processes can be analysed by capacitance and loss conductance measurements. This paper discusses key issues in the design of a capacitance/loss conductance transducer including the demodulation stage. Two methods to calculate capacitance and loss conductance, from the real and imaginary parts of the measured signal are presented. Finally a procedure to estimate the required cut-off frequency, order and component tolerance of the low-pass filter is suggested.


Keywords Impedance measurement, Phase-sensitive demodulator, Low-pass filter, Electrical tomography


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