1,720,987 research outputs found
A sensor system for oil fraction estimation in a two phase oil-water flow
No full textAbstractA sensor system for the study of an oil-water flow in a pipe is proposed. The purpose is to estimate the area fraction occupied by each fluid in a given section of the pipe, taking advantage of their different permittivity. The estimation is done by capacitance measurements between electrodes flush-mounted on the external surface of a nonconductive section of the pipe. A key contribution of the present work is to propose a solution based on a appropriate sensor head and tailored electronic interface to the problem of capacitive sensing in presence of conductive water which introduces parasitic coupling to stray elements outside the measurement section. The sensor system was designed, manufactured and experimentally tested. The results obtained for different fluid fractions and flow patterns were successfully compared with other reference methods
An experimental investigation and two-fluid model validation for dilute viscous oil in water dispersed pipe flow
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High sensitivity capacitance probe for liquid and gas dispersions in a conductive liquid.
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Capacitance sensor for hold-up measurement in high-viscous-oil/conductive-water core annular flows
No full textCapacitance sensors are widely used in multiphase flows, for example, to estimate the hold-up in a given section of the pipe, taking advantage of the different permittivity values of the two liquids. The estimation is obtained by capacitance measurements between two electrodes, flush mounted on the external surface of the experimental pipe. Usually, capacitance sensors are used to investigate flows with non-conductive fluids, but they have the possibility to work also when, for example, conductive water is used. However, the capacitance technique applied to conductive fluids develops some issues. In this paper, we present a concave electrode sensor system developed for oil/conductive-water flows. A key contribution is to propose a modelization to the problem of capacitive sensing in presence of conductive fluids, based on a new approach to the parasitic couplings outside the measurement section. Thanks to this modelization, we propose a new design method for the working frequency and the electrode measurement head
Electronic technique and circuit topology for accurate distance-independent contactless readout of passive LC sensors
No full textContactless readout of passive LC sensors composed of a capacitance sensor connected to a coil can be performed through a readout coil electromagnetically coupled with the sensor coil. Resonant frequency and quality factor can be extracted from the impedance measured at the readout coil by a technique which results theoretically independent of the coupling, and, therefore, the distance between the readout and the sensor coils. However, the effect of the unavoidable parasitic capacitance connected to the readout coil introduces in practice an undesired dependence of the measured values on the distance between the coils, resulting in a decreased accuracy. In this paper, such dependence is predicted by the results of a numerical analysis and experimentally verified. To overcome this limitation, a novel electronic technique and circuit topology for the compensation of the readout parasitic capacitance is proposed. The experimental results show that the compensation technique allows to read the resonant frequency of a LC pair at around 5.3 MHz with a variation of less than 200 ppm across an interrogation distance between 2 and 24 mm
Printed Coil on Quartz Crystal Resonator Sensor for Electromagnetic Contactless Interrogation
No full textThis paper presents a novel quartz crystal resonator (QCR) sensor, which embeds a conductive planar coil connected to the QCR electrodes that enables electromagnetic contactless interrogation techniques. The planar coil and the QCR electrodes are printed on a 330 μm-thick bare piezoelectric quartz crystal exploiting the aerosol-jet printing technology. The printed coil acts as the secondary coil of a pair of coupled inductors, allowing for a self-contained sensing element which avoids the need to connect an external coil for interrogation. The adopted interrogation technique, which advantageously enables distance-independent operation, is based on the measurement of the reflected impedance of the QCR sensor through the planar primary coil of the coupled inductors. The resonant frequency of the QCR has been measured without contact using the primary coil connected to an impedance analyser. The measured resonant frequency is 4.790260 MHz, and has a maximum deviation of about 50 Hz, i.e. 10.5 ppm, with respect to reference measurements taken via contact probes. Contactless operation distances up to 12.2 mm have been obtained
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