Novel Solution for Multi-Phase Semi-Cylindrical Capacitive Sensors

An accurate theoretical formulation is presented for a semi-cylindrical parallel plate capacitor, independent of the electrode dimensions. An approximate solution is also presented to relate the changes in capacitance with changing volume-ratio of the multi-phase dielectric filling of the capacitor. Two applications are considered to verify the proposed techniques. In the first application, the calculated capacitance is compared with the measured capacitance of a healthy tree trunk to identify the initial stage of pest infestation. In the second application, an approximate capacitance of a three-phase mixture, consisting of gas, oil and brine layers, are used to identify the phase-fraction of a petroleum carrying pipeline with a steady-state flow. The advantage and limitations of the proposed approximate method are studied. In addition to logging and monitoring the oil supply, this simple method can electronically control multi-phase pipes with intravenous injections to collect postoperative fluids from the human body.