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Abstract

Two methods are described for the direct measurement by on-line computer technique of the responses of the lumped circuits and solid polymer dielectrics at low frequencies. The first method involves the direct application of the step-voltage to the dielectric sample and the measurement of subsequent transient currents. The second method, a unique computer-aided measurement technique, involves the application of the ideal low-pass filter step-response, generated by the computer, to the dielectric sample and the measurement of its response. Both methods required a very sensitive electrometer amplifier to be constructed in order to detect the response. These responses are then sampled and stored by an on-line computer which then proceeds to evaluate their Fourier transforms.

Discrete Fourier transformation within the computer allows the data to be presented immediately, in various ways which are of direct use to the experimenter. The disadvantages of any previous assumptions about the nature of the dielectric response and the necessity for relatively crude approximations, which characterise the methods previously employed, are eliminated.

Apart from being new and original, especially in its use of non-causal response functions, the second method provides an excellent example of the power of the laboratory on-line computer technique and paves the way for special digital instruments to perform dielectric measurements. The sort of microprocessor which are now becoming available would allow such an instrument to be produced fairly cheaply and simply.

The results obtained are compared against those of previous workers, and an attempt is made to justify them on the basis of molecular theory.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QA Mathematics > QA75 Electronic computers. Computer science T Technology T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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