Cylindrical Sensor Research Articles

Propagation of electromagnetic fields in bulk terahertz metamaterials: A combined experimental and theoretical study

The availability of novel technologies that enable the fabrication of bulk metamaterials made it necessary to develop a theoretical language to discuss their properties appropriately. Here we use the fundamental Bloch mode approximation to explore bulk properties of metamaterials that operate at terahertz frequencies. We demonstrate that this approximation is valid in the case of terahertz meta-foil metamaterials. While relying on theoretical and experimental results, we show that the fundamental Bloch mode approximation can explain minuscule details that are unique to the bulk metamaterial. Various applications such as cylindrical lenses, terahertz cloaks, and sensors will benefit from our analysis.

Time Constant Estimates for Radiosonde Temperature Sensors

Abstract To correct time lag errors in radiosonde temperatures the sensor time constant has to be known. Time constants are not published for some widely used sensors and, in some cases, available time constants disagree. This study focuses on ML-405, ML-419, VIZ/Sippican Mark II Microsonde and B2, Russian MMT-1, and Chinese GZZ-7 rod thermistors. It measures still air time constants and heat capacities and derives theoretical still air and aerated time constants based on heat transfer involving nonuniform cylinders. With low aeration, such as in the stratosphere, heat conduction by lead wires from the thermistor noticeably shortens the time constant. Some discrepancies in published time constants are explained by researchers not considering the temperature dependence of all relevant variables. Empirical formulas are derived to estimate the aerated time constant of cylindrical temperature sensors based on dimensions. The aerated time constant in soundings is found to be about 6 times as long at 10 hPa as near sea level.

Design and Development of Liquid Level Transmitter using an Improved Linearized Network

In this paper, a liquid level transmitter using cylindrical capacitive sensor and an improved linearized network for capacitance measurement has been proposed to measure the liquid level and to convert level changes into an electrical current which can be transmitted to a remote indicator. The change in capacitance of cylindrical capacitive sensor due to change in liquid level is measured by an improved linearized capacitance measuring network. The offset capacitance of the cylindrical capacitive sensor and the stray capacitances that exist between sensor electrodes & metallic tank are measured before the liquid level measurement. The measured capacitances are used in the proposed capacitance measuring network to minimize the effects of offset capacitance and stray capacitances on liquid level measurement using dc control voltage and operational amplifiers with high input impedance. The experimental investigations have been performed to sense water level of metallic tank in both increased and decreased level conditions. In the first phase of experiment, a linearized network has been simulated using LabVIEW (laboratory virtual instrument engineering workbench) and studied with the test capacitance, and in the second phase, the experimentation was done by replacing the test capacitance with a cylindrical capacitive sensor for the measurement of liquid level. As a result of investigations conducted, it has been observed that the variation in liquid level from 0 to 25cm having linear relationship with output dc voltage in the range of 0 to 5.5V. Corresponding to liquid level variations, the dc output voltage further converted into an electric current of 4 to 20mA for remote indication and control purpose. The experimental results of liquid level transmitter are found to have good linearity of about ± 0.2% and a resolution of about 1 cm. The sensitivities of the capacitance measuring circuit and level transmitter have been found about 6.5 mV/pF and 250mV/cm respectively.

Elastic analysis of exponentially graded piezoelectric cylindrical structures as sensors and actuators

An analytical solution is obtained for functionally graded piezoelectric cylindrical structures, and the electroelastic behavior is investigated. The material properties are assumed to vary as an exponential function along the radial direction of the cylinder. The cylindrical structure acts as sensor or actuator and is subjected to mechanical and electrical loads at its inner and outer cylindrical surfaces. Based on the linear piezoelectricity theory, the governing equation in terms of the radial displacement is obtained as a second-order nonhomogeneous ordinary differential equation with variable coefficients, and its solution is obtained by the Frobenius series method. The illustrative examples show that the material nonhomogeneity has significant effect on the electroelastic fields of functionally graded piezoelectric cylindrical sensors and actuators.

Moisture content prediction of Iranian wheat using dielectric technique.

The moisture measurement is the most important criteria in harvesting and post harvesting processing of wheat. This paper investigates the moisture dependent dielectric constant and calibration equation of three most cultivated wheat varieties in Iran. An instrument with a cylindrical capacitive sensor was used to measure the dielectric constant of grain at different moisture contents. Samples were prepared at five levels of moisture content. To validate the proposed equations, the dried material dielectric constant was estimated and compared with the measured ones. Homographic regression models showed an acceptable prediction of dried wheat dielectric constant. Results showed that the calibration equation obtained for Shahriar variety was able to predict the moisture content of other varieties confidently. The lowest value of R (2) = 0.985 between predicted and reference moisture content for Tajan variety is still a good result.

소나 송신기의 회전 송신빔 구동을 위한 효율적인 출력 제어 기법 연구

본 논문은 능동 소나 송신기의 효율적인 회전 송신빔 구동을 위하여 부하인 원통형 배열센서의 회전 방위별 동적 임피던스 특성을 실험적으로 분석하고 최대 전력이 부하에 효과적으로 전송되도록 송신기의 출력을 실시간으로 제어하는 기법에 관한 연구이다. 회전 송신빔 구동시, 전기적, 음향적 경계조건에 의해 발생하는 과부하 조건에서 배열센서의 실시간 임피던스 변화와 송신기의 출력 거동 특성을 분석하였다. 그 결과로부터 과도 특성에서도 송신 중단 없이, 송신기와 부하를 보호하면서 송출되는 전력량을 최대화할 수 있는 새로운 송신 출력 제어 기법을 제안하고 실험을 통하여 제안된 기법을 검증하였다. This paper presents a study on the experimental analysis of the impedance characteristics according to the rotational direction of the transmission beam of a cylindrical sensor array. Besides, this suggests a real time control technique of the transmitter output for the effective maximum power transmission, in order to drive efficiently the rotational transmission beam of the active sonar transmitter. The output characteristics of the transmitter and the real-time impedance variations of the sensor array are analyzed under the overload conditions. They are caused by electric and acoustic boundary conditions when the rotational transmission beam is operated. From these results, a new output control method of the transmitter is proposed to protect the transmitter and its loads. It can maximize the output power without the transmission pause even if the transient phenomena occur. The proposed technique is verified from the experiment.

Investigation of water electrical parameters as a function of measurement frequency using cylindrical capacitive sensors

In this study electrical properties of different water liquids at frequency range of 100–2000Hz are investigated by using the short invasive and non-invasive cylindrical capacitive sensors (CCSs). Operation of the capacitance measurement module for such probes is based on the auto balancing bridge method. Comparison of the measured capacitances and measured resistances for different water liquids shows decrease by increasing the frequency. In another study the dielectric constant of distilled water, mineral water, tap water and salt water are measured. The effects of the frequency on the resistivity, permittivity and conductance of the different water liquids are also investigated.

A combined tactile and Raman probe for tissue characterization—design considerations

Histopathology is the golden standard for cancer diagnosis and involves the characterization of tissue components. It is labour intensive and time consuming. We have earlier proposed a combined fibre-optic near-infrared Raman spectroscopy (NIR-RS) and tactile resonance method (TRM) probe for detecting positive surgical margins as a complement to interoperative histopathology. The aims of this study were to investigate the effects of attaching an RS probe inside a cylindrical TRM sensor and to investigate how laser-induced heating of the fibre-optic NIR-RS affected the temperature of the RS probe tip and an encasing TRM sensor. In addition, the possibility to perform fibre-optic NIR-RS in a well-lit environment was investigated. A small amount of rubber latex was preferable for attaching the thin RS probe inside the TRM sensor. The temperature rise of the TRM sensor due to a fibre-optic NIR-RS at 270 mW during 20 s was less than 2 °C. Fibre-optic NIR-RS was feasible in a dimmed bright environment using a small light shield and automatic subtraction of a pre-recorded contaminant spectrum. The results are promising for a combined probe for tissue characterization.

Making an acoustic sensor undetectable with a pair of single-negative materials

We have proposed a two-dimensional cylindrical multi-layers device which can make a cylindrical acoustic sensor undetectable when the thickness of each layer of our device is much smaller than the wavelength of the incident wave. Our device only consists of a pair of complementary isotropic single-negative materials instead of double-negative ones. The parameters of materials in the device are homogenous and independent of those of host material as well as the cloaked object. Full wave simulations by finite element method are performed to verify the feasibility of the device. This proposal would greatly reduce the difficulty in both experimental design and fabrication.

수중폭발에 의한 원통형 배열센서의 구조 응답 및 안정성 해석

This paper establishes a modeling and simulation procedure for structural response and reliability of a cylindrical array sensor on submarines under the shock generated by underwater explosion. The structural reliability of SONAR is important because the submarine could get out of combat ability by the structural damage of the SONAR upon explosion. A cylindrical array sensor was first modeled using the finite element method. Modal analysis was then performed for the check of the reliability of the modeling. The shock resistance simulations were performed for the responses to the structural shock waves and for the responses to the directly applied underwater shock waves, according to BV-043 and MIL-STD-901D, respectively. The stresses of the structure were evaluated with von-Mises scheme. Vulnerable regions were exposed through mapping the maximum stress to the structural model. Maximum stress of the SONAR was compared with the yield stress of the material to examine the structural reliability.

Calibration of Electric Field Sensors Onboard the Resonance Satellite

Strategies and results for calibrating electric field sensors (antennas), as used in radio astronomy, onboard the spacecraft “Resonance” are presented. Calibration is performed for four boom antennas and four cylindrical sensors at the boom tips. These antennas are devised for the measurement of electric fields and plasma parameters. It is shown that the electrical representations of the antennas, the effective length vectors, differ from their mechanical originals and are shortened and tilted by several degrees of angle. The knowledge of the acquired parameters is of great benefit to the Resonance mission. In particular, goniopolarimetry techniques like polarization analysis and direction finding depend crucially on the effective axes. For the first time, this kind of analysis is performed for a space-borne antenna system consisting of boom monopoles and cylindrical tip antennas.

921 円筒型センサホルダを用いたC-FBGセンサによるAE波の検出に関する研究(GS-4 機械材料,特性の測定)

921 円筒型センサホルダを用いたC-FBGセンサによるAE波の検出に関する研究(GS-4 機械材料,特性の測定)

Error analysis of a new cylindrical capacitive sensor (CCS) for measuring five-dimensional motions of a rotor

Cylindrical capacitive sensor (CCS) refers to a class of displacement sensors that uses its whole circumference as sensing electrodes and conventional CCS’s usually measure the radial error motion of a rotor. In this paper, we propose a new smart sensor system that can measure the complete five-dimensional motions of a rotating shaft by combining two radial CCS’s and a specially designed target rotor. Due to the smaller number of sensors compared to the degrees of freedom to be measured, the sensor signals are susceptible to measurement errors such as the nonlinear errors and the cross talks. This paper presents a comprehensive error analysis of the proposed five-dimensional CCS. The result of error analysis is then used to come up with appropriate compensation methods for the nonlinearity and the cross talk of the proposed CCS. Simulation results are presented to verify the mathematical models for the measurement errors and also to validate the proposed compensation methods.

Comparison of invasive and non-invasive cylindrical capacitive sensors for electrical measurements of different water solutions and mixtures

In this study design and operation of invasive and non-invasive cylindrical capacitive sensor (CCS) designs for the electrical measurements of water, water solutions, and water mixtures are reported. Operation of the capacitance measurement module for such probes is based on the charge/discharge method. The measured capacitances and resistances for distilled water, mineral water, tap water and salt water samples are reported by using two sensor types and results are compared. The measured capacitance by invasive CCS for distilled water is about 2.28 μF and by non-invasive CCS is 31.40 pF, which shows a big difference for different probes. Such a difference is due to the electrical conductivity effects on the invasive CCS, which can be used for the conduction study of different liquids. In another study the capacitance values of a binary solution of water plus additive liquids such as antifreeze, petroleum, ethanol, methanol and mixtures of water with fresh and used motor oils are measured. The effects of the guard ring electrodes, and electrode–liquid interactions on the capacitance/resistance measurements for the invasive CCS filled with different water liquids are also investigated.

Effects of the rotor obliquity on the cylindrical capacitive sensor

The cylindrical capacitive sensor (CCS) is superior to conventional probe-type sensors in measuring the radial error motion of a rotor accurately since the CCS is immune to geometric errors of the rotor. However, due to the extended axial length of the CCS, the obliquity (or the axial tilt) of the rotor may cause unnecessary measurement error. This paper presents the effects of rotor obliquity on the performance of the CCS. The existing analytical model for the CCS has been extended to incorporate the axial tilt of the rotor, which leads to a new mathematical model for the CCS that can describe the complete three-dimensional motion of the rotor. Based on the new mathematical model, a nonlinear analysis is performed to derive the analytical solution of the measured rotor displacement with the CCS. As a result, it has been revealed how the rotor obliquity causes measurement errors in both eccentricity and phase angle. The analytical results are compared and verified with simulations.

Viscometer using drag force measurements

A robust and precise viscometer using the forces exerted by a laminar flow inside a small duct is presented: the force is measured on a long cylindrical sensor dipped into the flow. Two devices of respective volumes 1.4 and 0.031 ml have been realized, demonstrating that the technique is usable with small fluid volumes. Several Newtonian and non-Newtonian fluids have been tested at shear rates ranging from 0.3 to 10 s(-1) for the first device and from 85 to 2550 s(-1) for the second one. For Newtonian fluids, of viscosities ranging from 10(-3) to 0.1 Pa s, the linear response of the device has been verified and a 90% agreement with the values provided by commercial rheometers is obtained. For non-Newtonian polymer solutions, the variation of the force with the flow velocity allows one to determine the dependence of the viscosity on the shear rate. Two shear thinning polymer solutions with a power law behavior at intermediate shear rates have been investigated and their rheological parameters have been determined.

Development of cylindrical hot-film sensors for measuring instant velocity of fluid flow

The cylindrical hot-film sensor has found wide industrial application because it combines the high frequency response with improved strength and stability. In this work, such sensors were fabricated for application in different fluids. The sensing part of the sensor consisted of a nanostructured sandwich with a 40–60 nm thick nickel film deposited by PVD process onto a 125 micrometer diameter cylindrical quartz wire. An outer 0.5 or 2 micrometer thick protective silica layer was applied onto the nickel film. The sensors obtained were subjected to various functional and quality assessment tests. Using a constant temperature anemometry (CTA) circuit, the sensors were calibrated conforming to well-known procedures. Furthermore, an evaluation of the sensor response was undertaken by measuring an already known turbulent flow and comparing the results with those of the literature. Finally, technical conclusions were drawn from the results.

CFD evaluation of thermal convection inside the DACON convection sensor in actual space flight

A CFD(Computational Fluid Dynamics) model has been developed using the commercial CFD package FLUENT for the thermal convection inside air filled cylindrical DACON sensor, where the onboard time dependent gravitational micro acceleration has been considered. Time dependent, curve fitted gravitational accelera-tion in x- and y-axes from published data have been incorporated in FLUENT through a User Defined Function (UDF), developed in C which includes space craft rotation. At the sensor plane the two-dimensional flow has also been visualized. A good agreement is between simu-lation and published experimental data. Last but not the least, for checking its response to suffi-ciently strong perturbations in an orbital flight, physical and numerical experiments are carried out where an astronaut swung the sensor in hands along the y axis with amplitude of 10cm and a frequency of 0.2 Hz. A good qualitative validation has been achieved between CFD and actual experimental results.

CRLH-TL Sensors for Flow Inhomogeneties Detection of Pneumatic Conveyed Pulverized Solids

This paper presents an application of a Composite Right/Left-Handed (CRLH) Transmission Line resonator for a compact mass flow detector which is able to detect inhomogeneous flows. In this concept, series capacitors and shunt inductors are used to synthesize a medium with simultaneously negative permeability and permittivity – the so called metamaterial. The helix shape of the cylindrical CRLH-TL sensor offers the possibility to detect flow inhomogeneities within the pipeline which can be used to correct the detected massflow rate. A combination of two CRLH-TL structures within the same cross-section of the pipeline can improve the angular sensitivity of the sensor. A prototype was realized and tested in a dedicated measurement setup to prove the concept.

Active optics null test system based on a liquid crystal programmable spatial light modulator

We present an active null test system adapted to test lenses and wavefronts with complex shapes and strong local deformations. This system provides greater flexibility than conventional static null tests that match only a precisely positioned, individual wavefront. The system is based on a cylindrical Shack-Hartmann wavefront sensor, a commercial liquid crystal programmable phase modulator (PPM), which acts as the active null corrector, enabling the compensation of large strokes with high fidelity in a single iteration, and a spatial filter to remove unmodulated light when steep phase changes are compensated. We have evaluated the PPM's phase response at 635 nm and checked its performance by measuring its capability to generate different amounts of defocus aberration, finding root mean squared errors below λ/18 for spherical wavefronts with peak-to-valley heights of up to 78.7λ, which stands as the limit from which diffractive artifacts created by the PPM have been found to be critical under no spatial filtering. Results of a null test for a complex lens (an ophthalmic customized progressive addition lens) are presented and discussed.