Abstract：The capacitance changes is very small and difficult to measure for electrical capacitance tomography (ECT),and the total stray capacitance is much larger than the measured capacitance. In this paper three types of low value capacitance measuring circuits, which are most suitable for the use in ECT system,-four kinds of circuits such as the AC based circuit with feedback compensation, and the self-balancing-capacitance measuring circuit are described. The stray-immune problem of capacitance measurement is discussed. Their advantages and disadvantages are also compared.
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