Cylindrical Capacitor Research Articles

A multi-channel capacitive probe for electrostatic fluctuation measurement in the Madison Symmetric Torus reversed field pinch.

A 40-channel capacitive probe has been developed to measure the electrostatic fluctuations associated with the tearing modes deep into Madison Symmetric Torus (MST) reversed field pinch plasma. The capacitive probe measures the ac component of the plasma potential via the voltage induced on stainless steel electrodes capacitively coupled with the plasma through a thin annular layer of boron nitride (BN) dielectric (also serves as the particle shield). When bombarded by the plasma electrons, BN provides a sufficiently large secondary electron emission for the induced voltage to be very close to the plasma potential. The probe consists of four stalks each with ten cylindrical capacitors that are radially separated by 1.5 cm. The four stalks are arranged on a 1.3 cm square grid so that at each radial position, there are four electrodes forming a square grid. Every two adjacent radial sets of four electrodes form a cube. The fluctuating electric field can be calculated by the gradient of the plasma potential fluctuations at the eight corners of the cube. The probe can be inserted up to 15 cm (r/a = 0.7) into the plasma. The capacitive probe has a frequency bandwidth from 13 Hz to 100 kHz, amplifier-circuit limit, sufficient for studying the tearing modes (5-30 kHz) in the MST reversed-field pinch.

The Differential Method for Force Measurement Based on Electrostatic Force

The small force measurement is very important with development of the technology. The electrostatic force is adopted, in which a pair of coaxial cylindrical capacitors generate the electrostatic force when a voltage is applied across the inner and outer electrodes. However, the measured force will be covered by noise (creep, ground vibration, and air flow) and could not be measured accurately. In this paper, we introduce the differential method to reduce the effect of noise. Two identical parallelogram mechanisms (PM) serve as the mechanical spring. One of the PM serves as the reference and another serves as the force sensor. The common signal will be offset, and the difference signal will serve as output. In this way, the effect of the creep will be reduced. The measurement system of the electrostatic force was characterized by applying mechanical forces of known magnitude via loading weights of calibrated masses. The uncertainty from voltage, laser interferometer, and capacitance gradient was estimated. For the measured force, the relative uncertainty is less than 4% (kp=2).

Characterization of a Capacitive Position Sensor for a Miniaturized Hydraulic Actuator

Novel surgical techniques require laparoscopic instruments which are intelligent micro-manipulators rather than simple manually operated scissors. Hydraulic drives, with their high force and power density, and low weight are the perfect candidates to drive these new laparoscopic instruments. However, their use in intelligent systems requires the integration of a displacement measurement technology to ensure controllability. The aim of this paper is the characterization and miniaturization of a capacitive sensor that can be integrated into the hydraulic drives in order to improve the precision of the instrument’s positioning. The proposed sensor solution is structurally integrated into the hydraulic drive, using its barrel and rod as a coaxial cylindrical capacitor, so that no additional sensor needs to be integrated. The performance of the proposed solution has been examined using FEA simulations of a mini and a miniaturized cylinder design. The simulation has been validated experimentally and the results are in good agreement. The results showed a linear relationship between capacitance and displacement with a precision of $\pm 27~\mu \text{m}$ , thus proving the feasibility of the method.

High Performance Cylindrical Capacitor as a Relative Humidity Sensor for Wearable Computing Devices

First, we designed and fabricated a cylindrical humidity sensing capacitor. In addition, we suggested its suitability as a capacitive RH sensor for wearable computing devices. Aluminum (Al) thin film for electrodes was uniformly deposited on a single fiber that consists of one fiber. The exposed area of the polyimide (PI) was particularly situated on an outer electrode to promote its moisture sensing capability. The capacitance change according to the relative humidity is indicated with a specific S-shape due to the interval adsorption reactions between the imide group and the water molecules. An adsorption mechanism is proposed based on the theory of the volume filling of micropores (TVFM), and the effect of PI thickness was investigated. In addition, the response times for adsorption and desorption were measured by changing the moisture condition. Moreover, with a repetitive bending test, the device durability was inspected by implementing the bending times and bending curvature radius.

Precise Computation of the Capacitance of a Cylindrical Capacitor Using the Method of Moments

Due to the fringing effect, the capacitance per length of a cylindrical capacitor of finite length is bigger than that of an infinitely long cylindrical capacitor. To examine the fringing effect on the capacitance of a cylindrical capacitor of finite length, the method of moments is employed to precisely compute the capacitance. In order to verify the computation results of the method of moments, COMSOL is also used to find the capacitance. The developed program based on the method of moments is applied to the accurate computation of capacitances of a cylindrical type of Blumlein pulse forming line.

In Vitro Study of a Superhydrophilic Thin Film Nitinol Endograft that is Electrostatically Endothelialized in the Catheter Prior to the Endovascular Procedure.

Electrostatic endothelial cell seeding has evolved as an exceptional technique to improve the efficiency of cell seeding in terms of frequency of attached cells and the amount of cell adhesion for the treatment of vascular diseases. In the recent times, both untreated and superhydrophilic thin film nitinol (TFN) have exhibited strong prospects as substrates for creation of small-diameter endovascular grafts due to their hallmark properties of superelasticity, ultra low-profile character, and grown hemocompatible oxide layer with the presence of a uniform endothelial layer on the surface. The purpose of the current study is to understand the effects of endothelial cell seeding parameters (i.e., applied voltage, incubation time, substrate chemistry, and cell suspension solution) to investigate the cell seeding phenomenon and to improve the cell adhesion and growth on the TFN surface under electrostatic transplantation. Both parallel plate and cylindrical capacitor models were used along with the Taguchi Design of Experiment (DOE) methods to design in vitro test parameters. A novel in vitro system for a cylindrical capacitor model was created using a micro flow pump, micro incubation system, and silicone tubings. The augmented endothelialization on thin film nitinol was developed to determine the effect of cell seeding and deployed in a 6 Fr intravascular catheter setup. Cell viability along with morphology and proliferation of adhered cells were evaluated using fluorescent and scanning electron microscopy. Our results demonstrated that the maximum number of cells attached on STFN in the catheter was observed in 5 V with the 2 h exposure of in the cell culture medium (CCM) solution. The condition showed 5 V voltage with 0.68 × 10−6 µC electrostatic charge and 5.11 V·mm−1 electric field. Our findings have first demonstrated that the electrostatic endothelialization on the superhydrophilic thin film nitinol endograft within the catheter prior to the endovascular procedure could enhance the biocompatibility for low-profile endovascular applications.

Thermo-electro-hydrodynamic convection under microgravity: a review

Recent studies on thermo-electro-hydrodynamic (TEHD) convection are reviewed with focus on investigations motivated by the analogy with natural convection. TEHD convection originates in the action of the dielectrophoretic force generated by an alternating electric voltage applied to a dielectric fluid with a temperature gradient. This electrohydrodynamic force is analogous to Archimedean thermal buoyancy and can be regarded as a thermal buoyancy force in electric effective gravity. The review is concerned with TEHD convection in plane, cylindrical, and spherical capacitors under microgravity conditions, where the electric gravity can induce convection without any complexities arising from geometry or the buoyancy force due to the Earth’s gravity. We will highlight the convection in spherical geometry, comparing developed theories and numerical simulations with the GEOFLOW experiments performed on board the International Space Station (ISS).

Method for extrapolating the compressibility data of solids from room to lower temperatures

Around room temperature, the elastic constants of solids can be measured comfortably applying commercial equipment, e.g., resonant ultrasound spectroscopy devices, whereas at low temperatures special efforts are necessary. To decrease the effort, a method has been developed and tested for extrapolating data on the compressibility of solids to lower temperatures. The method is based on well-known approximate relations between the thermodynamic properties of solids, the derivation of which was pioneered by Gruneisen, and the measurement of quantities, which are easier accessible experimentally than the elastic constants (thermal expansion, specific heat). In essence, the extrapolation uses data for the thermal expansion. The applicability of the method has been tested for copper, the properties of which are documented comprehensively in literature even at low temperatures. In a second step, the method has been applied to extrapolate the compressibility data of a copper-beryllium-cobalt alloy from near room temperature down to about 80 K with a relative uncertainty of order 0.1%. This extrapolation is needed for and verified by dielectric-constant gas thermometry, a special kind of primary thermometry for determining thermodynamic temperatures. For such gas-thermometry experiments cylindrical capacitors, the electrodes of which have been made from the investigated copper beryllium alloys, are used.

Bose–Einstein condensation in a vapor of sodium atoms in an electric field

Bose–Einstein condensation (BEC) at normal temperature (T=343K) has been observed because an electric field was first applied. There are two ways to achieve phase transition: lower the temperature of Bose gas or increase its density. This article provides more appropriate method: increase the voltage. In theory, 3s and 3p states of sodium are not degenerate, but Na may be polar atom doesnot conflict with quantum mechanics because it is hydrogen-like atom. Our innovation lies in we applied an electric field used for the orientation polarization. Na vapor was filled in a cylindrical capacitor. In order to determine the polarity of sodium, we measured the capacitance at different temperatures. If Na is non-polar atom, its capacitance should be independent of temperature because the nucleus of atom is located at the center of the electron cloud. But our experiment shows that its capacitance is related to temperature, so Na is polar atom. In order to achieve Na vapor phase transition, we measured the capacitance at different voltages. From the entropy of Na vapor S=0, the critical voltage Vc=68volts. When V<Vc, many atoms are in random orientation S>0; when V>Vc, the atoms become aligned with the field S<0, phase transition occurred. When V=390volts »Vc, the capacitance decreased from C=1.9C0 to C≈C0 (C0 is the vacuum capacitance), this result implies that almost all the Na atoms (more than 98%) are aligned with the field, Na vapor entered quasi-vacuum state. We create a BEC with 2.506×1017 atoms, condensate fraction reached 98.9%. This is BEC in momentum space. Our experiment shows that if a Bose gas enters quasi-vacuum state, this also means that it underwent phase transition and generates BEC. Therefore, quasi-vacuum state of alkali gas is essentially large-scale BEC. This is an unexpected discovery. BEC and vacuum theory are two unrelated research areas, but now they are closely linked together. The maximum induced dipole moment dind≤7.8×10−15ecm can be neglected. Ultra-low temperature is in order to make Bose gas phase transition, we achieve the phase transition by the critical voltage, so the ultra-low temperature is not necessary. According to the standard proposed by Ketterle, although we didn’t use laser cooling atoms, our experiment is real ideal BEC. Na material with purity 99.95% was supplied by Strem Chemicals Co., USA. Our experiments are easily repeated because low temperature is not necessary.

Highly sensitive, precise, and traceable measurement of force

ABSTRACTForce in the micronewton range may be traced to the International System of Units by an electrostatic force balance weight system. However, there is a conflict between range and sensitivity. To solve this problem, a lever-type force metrology system based on the null-balance method is reported. The force is loaded on one end of the lever, causing elastic torsion of the central rod, and an electrostatic force is applied to the other end. With a variety of mass loading positions and standard weights, a wide range of moments may be produced to calibrate the system. The electrostatic force was generated by a pair of coaxial cylindrical capacitors where the applied voltage was converted into electrode displacement. The design of the inner and outer cylindrical capacitors was deduced considering the material and miniaturization requirements, and concentric alignment was ensured by a vision system. The null balance was achieved by a proportion-integration-differentiation control system, so that the external force was compensated by the electrostatic force. A method to increase the center of gravity was used to improve the resolution. The mechanism was analyzed based on stiffness, strength, stability, and frequency. Furthermore, the impact on the capacitance gradient due to the capacitor tilt caused by the applied force was estimated. Standard weights were utilized to evaluate the system performance. The results showed that a stiffness of 0.8 N/m and a force resolution of 10−8 N were achieved.

Large-Scale Bose-Einstein Condensation in a Vapor of Cesium Atoms at Normal Temperature (T=353K)

Large-scale BEC of cesium at T=353 K was first observed. Until now, scientists have applied magnetic fields and lasers, but never applied electric fields, and atoms are oriented at random, so observation of BEC is very difficult. Our innovation lies in the application of electric fields. We theoretically proved that alkali atom (include Cs) may be polar atom doesn't conflict with quantum mechanics. Variation of the capacitance with temperature offers a means of separating the polar and non-polar atom. Cs vapor was filled in cylindrical capacitor. Our experiment shows that Cs is polar atom because its capacitance is related to temperature. In the past, to realize the phase transition, ultralow temperature is necessary. But now we don’t require ultralow temperature, because we use the critical voltage Vc to achieve the phase transition. From the entropy S=Nk ln 2πe /a=0, a=dV/kTH =2πe, Vc ≈ 63volts. When V 0; when V >Vc, S < 0, phase transition occurred. When V=350 volts, the capacitance decreased from C=1.97C0 to C ≈ C0 (C0 is the vacuum capacitance), this result implies that almost all Cs atoms (more than 98.9%), like as dipoles, are aligned with the field. We create BEC with 1.928×1017 atoms, these atoms have the same momentum. Cs material with purity 99.95% was supplied by Strem Chemicals Co., USA. Both BEC and superconductivity are condensed in the momentum space, therefore these two kinds of condensation can’t be observed with the naked eye. When superconductivity occurs, the resistance R≈0, a simple and direct method to observe superconductivity is to measure the resistance by voltammetry. Similarly, when BEC occurs, the electric susceptibility χe=C/C0 –1 ≈ 0, a simple and direct method to observe BEC is to measure the capacitance by cylindrical capacitor. BEC is also a quasi-superconducting state.

Design of Thin Film Capacitive Sensor for Flow Measurement

We report the design methodology of thin film capacitor (TFC) device using thermal evaporation technique for quality study or material differentiation application by testing with liquid (different concentration) and solid. A simple and special modification was incorporated in thermal evaporation setup for depositing semi cylindrical capacitor design on a capillary tube (CT). In order to avoid the disturbance due to electrostatic noise disturbance, TFC was covered with another glass tube, aluminum (Al) metal foil (as shield) and finally by plastic tube cover. Electrodes were taken from the film using silvers paste and connected as input to the LCR-Z meter. The capacitance value of the thin film was varied up to 15-16 pF from the initial value (Al: 129 pF, Cu: 130 pF) when subjected to the static flow. A low cost embedded micro controller module with Liquid Crystal Display (LCD) was developed for the real time testing of TFC.

Fabrication of thermally evaporated Al thin film on cylindrical PET monofilament for wearable computing devices

During the initial development of wearable computing devices, the conductive fibers of Al thin film on cylindrical PET monofilament were fabricated by thermal evaporation. Their electrical current-voltage characteristics curves were excellent for incorporation into wearable devices such as fiber-based cylindrical capacitors or thin film transistors. Their surfaces were modified by UV exposure and dip coating of acryl or PVP to investigate the surface effect. The conductive fiber with PVP coating showed the best conductivities because the rough surface of the PET substrate transformed into a smooth surface. The conductivities of PET fiber with and without PVP were 6.81 × 103 Ω−1cm−1 and 5.62 × 103 Ω−1cm−1, respectively. In order to understand the deposition process of Al thin film on cylindrical PET, Al thin film on PET fiber was studied using SEM (Scanning Electron Microscope), conductivities and thickness measurements. Hillocks on the surface of conductive PET fibers were observed and investigated by AFM on the surface. Hillocks were formed and grown during Al thermal evaporation because of severe compressive strain and plastic deformation induced by large differences in thermal expansion between PET substrate and Al thin film. From the analysis of hillock size distribution, it turns out that hillocks grew not transversely but longitudinally.

A novel electrolyte used in high working voltage application for electrical double-layer capacitor using spiro-(1,1′)-bipyrrolidinium tetrafluoroborate in mixtures solvents

This paper is addressed on studying the electrolytes for electrical double layer capacitors with relatively high ionic conductivity and electrochemical stability for high energy density application. A systematic analysis of the electrochemical characteristics has been presented using spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBP-BF4) with 1.5molL−1 (M) in variety of solvent compositions including propylene carbonate (PC), ethylene carbonate (EC) and dimethyl carbonate (DMC), while the solvent mixtures are PC+DMC (1:1 in volume) and PC+DMC+EC (1:1:1 in volume). The physical properties and electrochemical performance of SBP-BF4-based electrolytes are improved by tuning solvent mixtures compositions for high working voltage application. The binary solvent system of PC+DMC electrolyte exhibits lowest viscosity of about 3.14 mPas, while the ternary solvent system of PC+DMC+EC electrolyte exhibits highest conductivity of about 18.08mScm−1. The SBP-BF4/PC-based electrolytes display excellent upper voltage hold capability about 3.5V. The binary solvent system exhibits superior rate performance, when the charge cut-off voltage is lower than 3.2V. The ternary solvent system exhibits superior rate performance than that of other two solvent systems electrolytes, when the charge cut-off voltage is higher than 3.2V. The maximum energy density and power density of EDLCs using the ternary solvent system electrolyte are 41.5Whkg−1 and 17.0kWkg−1, respectively. The spiral cylindrical capacitors based on ternary solvent system electrolyte exhibits better cycle performance than that of other two solvent system electrolytes at the high working voltages.

Comparison of Cable Insulation Control in Weak and Strong Electric Fields

In this paper the modern methods of cable products insulation control are referred. A comparison of efficiency of the cable insulation defects control by changing in cable area capacitance is carried out in the strong and weak electric fields. The electric cable can be represented as a cylindrical capacitor, but to simplify the issue the insulation area is represented as a plate capacitor with anisotropic dielectric. The cable insulation model is created in the software Comsol Multyphysic. The effect of the defect dimension on the cable area electric capacitance in a strong and weak electric field is described. Also, the control sensitivity of both methods was assessed and compared with each other. The control sensitivity in a weak electric field is slightly higher for the defects with small size (less than 70% from insulation thickness). The control sensitivity in a strong electric field is considerably higher for the defects with big size (more than 70% from insulation thickness).

Analysis of element free Galerkin interloping moving least square method in an electrostatic problem

The element free Galerkin (EFG) meshless method is very effective for solving electrostatic problems. However, it leads to shape functions which do not satisfy the Kronecher delta property. Therefore, it is necessary to use additional techniques to impose the essential boundary conditions (EBCs) and to treat the material discontinuities. In this work, the EFG method is used with interpolating shape functions. Therefore, the Kronecher delta property is satisfied, the EBCs are enforced directly in the discrete system, and the material discontinuities treatment is improved. The method is evaluated in the analysis of a cylindrical coaxial capacitor filled with two concentric and different dielectric materials where obtained results confirmed its efficiency. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1390–1395, 2015

Nondestructive Determination of Moisture Content in Dry Fruits by Impedance and Phase Angle Measurements

An electronic method to estimate the moisture content (MC) of dry fruits by measuring the impedance (Z) and phase angle (θ) of a cylindrical parallel-plate capacitor with dry fruit sample between the plates, using a CI meter (Chari’s Impedance meter) at 1 and 9 MHz is described. Capacitance C was derived from Z and θ, and using the C, θ, and Z values of a set of dried cherries, whose MC values were later determined by the vacuum hot air-oven method, a calibration equation was developed. Using this equation, and their measured C, θ, and Z values, the MC of a group of cherries, not used in the calibration, was predicted. The predicted values were compared with their air-oven values. Similar predictions were done using the same method on dried blueberries. The method worked well with a good R2 value, and showed a low standard error of prediction (SEP) in the measured MC range between 5% and 30% for cherries, and 9% and 22% for blueberries.

A capacitive angular sensor with flexible digitated electrodes

Purpose – This paper aims to present a prototype of a capacitive angular-position sensor which exploits advantages of flexible/printed electronics. The novelty of the sensor is that the capacitor structure is placed at the circumference of the rotor and stator, that it posses two channels (capacitor structures) electrically shifted for p/4 and that the rotor is common for both channels. The electrodes of the sensing capacitor are digitated, providing a triangular transfer function. Design/methodology/approach – This sensor prototype consists of two flexible inkjet-printed silver electrodes forming a cylindrical capacitor structure. One of them is wrapped around the stator and another is wrapped around the rotor part of a simple mechanical platform used to precisely adjust the angular displacement. Findings – The capacitance as a function of angular position was measured using an inductance capacitance impedance (LCZ) Meter, and results are presented for a full-turn measurement range. The experimental results are compared with analytical ones and very good agreement has been achieved. Originality/value – The proposed capacitive sensor structure can be used as an absolute or an incremental encoder with different resolutions, and it can be applied in automotive industry or robotics.

Development of the liquid level meters for the PandaX dark matter detector

The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase (liquid/gas) mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors that are custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and are recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations (standard deviations) of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few days of test operation.

Block Copolymer Ordering in Cylindrical Capacitors

We investigate the morphologies of block copolymers confined in the region between two concentric and charged cylinders. The relative stability of a concentric lamellar phase compared to one where the lamellae are oriented in the radial direction is determined from the competition between long-range elastic and electrostatic forces. We find in weak and strong segregation and by single-chain-in-mean-field simulations that under sufficiently strong voltage difference there is a phase transition from concentric to radial lamellae containing defects. Above a threshold voltage the block copolymer melt develops an interfacial instability at a finite wavelength.