A modified Schering bridge for measurement of the dielectric parameters of a material and the capacitance of a capacitive transducer
TL;DR: In this article, a modified operational amplifier-based Schering bridge network is proposed, where the effect of stray capacitance may be assumed to be negligible and continuous measurement is possible.
About: This article is published in Measurement.The article was published on 2003-01-01. It has received 16 citations till now. The article focuses on the topics: Mutual capacitance & Parasitic capacitance.
Citations
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TL;DR: In this paper, electric field induced director orientation of a nematic liquid crystal (LC)+ carbon nanotube (CNT) system reveals insights on switching behavior for this anisotropic composite.
Abstract: Electric field induced director orientation of a nematic liquid crystal (LC)+carbon nanotube (CNT) system reveals insights on switching behavior for this anisotropic composite. Once the field goes off, the LC+CNT system relaxes back to the original orientation through a mechanical rotation, revealing the intrinsic dynamics. LC molecules and CNTs cooperatively form local pseudonematic domains in the isotropic phase due to strong LC-CNT interactions. These field-responsive anisotropic domains do not relax back to the original orientation on switching of the field off, which could find potential applications in memory devices.
99 citations
TL;DR: The design of a non-intrusive system to measure ultra-low water content in crude oil is presented, based on a capacitance to phase angle conversion method, to ensure high immunity against temperature variation and background noise and eliminate phase jitter and amplitude variation of the main oscillator that could destabilize the output.
Abstract: This paper presents the design of a non-intrusive system to measure ultra-low water content in crude oil. The system is based on a capacitance to phase angle conversion method. Water content is measured with a capacitance sensor comprising two semi-cylindrical electrodes mounted on the outer side of a glass tube. The presence of water induces a capacitance change that in turn converts into a phase angle, with respect to a main oscillator. A differential sensing technique is adopted not only to ensure high immunity against temperature variation and background noise, but also to eliminate phase jitter and amplitude variation of the main oscillator that could destabilize the output. The complete capacitive sensing system was implemented in hardware and experiment results using crude oil samples demonstrated that a resolution of ±50 ppm of water content in crude oil was achieved by the proposed design.
65 citations
Additional excerpts
... Modified Schering Bridge network [17]....
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TL;DR: In this paper, a nematic liquid crystal (LC) can be used to template carbon nanotubes (CNTs) on a macroscopic dimension and the nematic director field coupled to the dispersed CNT long-axis enables controlled director reorientation using well-established methods of LC alignment techniques, such as patterned-electrode surface, electric fields, and magnetic fields.
Abstract: The self-organizing properties of nematic liquid crystals (LC) can be used to template carbon nanotubes (CNTs) on a macroscopic dimension. The nematic director field, coupled to the dispersed CNT long-axis, enables controlled director reorientation using well-established methods of LC alignment techniques, such as patterned-electrode-surface, electric fields, and magnetic fields. Electric field induced director rotation of a nematic LC+CNT system is of potential interests due to its possible applications as a nano electromechanical system. The relaxation mechanism for a LC+CNT composite, on the removal of the applied field, reveals the intrinsic dynamics of this anisotropic system. Dielectric hysteresis and temperature dependence of the dielectric constant coherently shows the ferroelectric-type behavior of the LC+CNT system in the nematic phase. The strong surface anchoring of LC molecules on CNT walls results in forming local isolated pseudo-nematic domains in the isotropic phase. These domains, being anisotropic, respond to external fields, but, do not relax back to the original state on switching of the field off, showing non-volatile memory effect.
51 citations
TL;DR: In this article, the authors investigated the dielectric properties of a nematic liquid crystal (LC) and carbon nanotubes (CNTs) composite system and found that the dielection relaxation on removing the applied field follows a singleexponential decay, exhibiting a faster decay response than the pure LC above a threshold field.
Abstract: Self-organizing nematic liquid crystals (LCs) impart their orientational order onto dispersed carbon nanotubes (CNTs) and obtain CNT-self-assembly on a macroscopic dimension. The nanotube-long axis, being coupled to the nematic director, enables orientational manipulation via the LC nematic reorientation. Electric-field-induced director rotation of a nematic LC+CNT system is of potential interest due to its possible application as a nanoelectromechanical system. Electric field and temperature dependence of dielectric properties of a LC+CNT composite system have been investigated to understand the principles governing CNT assembly mediated by the LC. In the LC+CNT nematic phase, the dielectric relaxation on removing the applied field follows a single-exponential decay, exhibiting a faster decay response than the pure LC above a threshold field. The observed dielectric behaviors on field cycling in the nematic phase for the composite indicates an electromechanical hysteresis effect of the director field due...
45 citations
TL;DR: In the proposed transducer, the use of a diaphragm-type DP cell is not needed, and thus, the problems associated with DP cell are avoided.
Abstract: The ordinary orifice transducer widely used in process industries for flow rate measurement produces a differential pressure which is generally measured by a DP cell and thus may suffer from various problems like leakage of process fluid, corrosion of diaphragm materials, etc In this paper, the design of a noncontact capacitance-type orifice transducer for the measurement of flow rate of a conducting liquid through a pipeline has been described In the proposed transducer, the use of a diaphragm-type DP cell is not needed, and thus, the problems associated with DP cell are avoided The theoretical analysis of the flow transducer is presented in this paper The performance of the flow transducer along with that of the signal conditioner for flow of tap water through a pipeline has been tested experimentally The experimental results are presented in this paper A good linearity and repeatability of the sensor capacitance, transducer output, and signal conditioner output with flow rate have been observed
33 citations
Cites background or methods from "A modified Schering bridge for meas..."
...Various works [1], [2], [8], [11], [12] have been reported to measure the very small change of capacitance of a capacitive sensor....
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...In this paper, a modified bridge network [12] has been utilized to measure the change in capacitance of the proposed flow sensor....
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References
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Book•
01 Jan 1983
TL;DR: In this paper, the authors present general principles of measurement systems, including reliability, choice and economics of measurement system elements, as well as the accuracy and reliability of the measurement system in the steady state.
Abstract: Part I: General Principles 1. The general measurement system. 2. Static characteristics of measurement system elements. 3. The accuracy of measurement systems in the steady state. 4. Dynamic characteristics of measurement systems. 5. Loading effects and two port networks. 6. Signals and noise in measurement systems. 7. Reliability, choice and economics of measurement systems. Part II: Typical Measurement System elements. 8. Sensing elements. 9. Signal conditioning elements. 10. Signal processing elements. 11. Data presentation elements. Part III: Speciaised Measurement Systems 12. Flow measurement systems. 13. Intrinsically safe measurement systems. 14. Heat transfer effects in measurement systems. 15. Optical measurement systems. 16. Ultrasonic measurement systems. 17. Gas chromatography. 18. Data acquisition. Answers to numerical problems. Index.
347 citations
"A modified Schering bridge for meas..." refers background or methods in this paper
...There are different bridge techniques [1,2,6,9,11,15] for measuring the capacitance, but the Schering bridge technique may,...
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...Perkin and Preston [2] have evaluated the effect of dc current on the secondary of a transformer....
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01 Jan 1999
TL;DR: In this article, the authors presented a highly sensitive AC-based capacitance measuring circuit, which has been specially designed for this purpose, and a PC-based ECT system with this circuit.
Abstract: Electrical capacitance tomography (ECT) is a new technology that is used to visualise the internal behaviour of industrial processes comprising dielectric components. A particular difficulty with capacitance measurement for tomography is that the stray capacitance to earth of an ECT sensor is large (/spl sim/150 pF) compared with the interelectrode capacitance to be measured (usually <0.5 pF), and the measurement range is wide (0.01-2 pF). The authors present a highly sensitive AC-based capacitance measuring circuit, which has been specially designed for this purpose, and a PC-based ECT system with this circuit. Experimental results show that this ECT system can measure as small as 0.01 pF capacitance with 0.0002 pF error, and could collect tomographic image data at more than 100 frames per second.
270 citations
TL;DR: This article summarizes principles of alternating current electrode polarization and techniques to Correct for Electrode Polarization.
Abstract: This article summarizes principles of alternating current electrode polarization The importance of alternating current electrode polarization in biological impedance studies is discussed The following topics are treated in detail: Definition of Electrode Polarization Impedance; Linearity and Superpositioning Principle; Frequency Dependence of Electrode Impedance; Preparation of Electrodes (Optimal current density for platinum black application, Stability of electrode impedance, Cell design for platinization purposes, Aging and cleaning of electrodes); Effect of Electrode Polarization on Biological Impedances; Effects of Biological Matter on Electrode Polarization; Techniques to Correct for Electrode Polarization (Electrode distance variation technique, Large electrode distance, Graphical technique, Substitution technique, Frequency variation technique, Four-electrode technique); Transient Response of Electrodes; Microelectrodes
176 citations
"A modified Schering bridge for meas..." refers background in this paper
...Various other attempts have been made to measure small capacitance of a transducer very accurately such as Capacitance to DC voltage Converter Tech nique [3], Charge Transfer Technique [10,13] and Circuit Theory Based Technique [14] etc....
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...Since the two cores are identical with identical windings, the cross-talk errors [11,14], due to the stray magnetic fields may be assumed to be identical in the two cores and hence they will be cancelled out in the resultant differential output....
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...Di Rienzo and co workers [11,14], have designed a circular array of hall probe sensors for busbar current measurement and estimated the cross-talk error of measurement due to other magnetic fields to lie within 0....
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TL;DR: In this article, a stray-immune capacitance measuring instrument based on the charge transfer principle is described, which has a programmable measurement frequency up to several megahertz and is inexpensive and suitable for integration onto a single chip.
Abstract: A stray-immune capacitance measuring instrument based on the charge transfer principle is described. It has a programmable measurement frequency up to several megahertz and is inexpensive and suitable for integration onto a single chip. The effects of stray capacitances, including those of the switching components, have been eliminated by using a special switching arrangement, resulting in a baseline drift of 0.02 pF (at 1-MHz measurement frequency) over a 12-h period. >
91 citations