Rectangular Sensor Research Articles

Theoretical study of in-plane response of magnetic field sensor to magnetic beads in an in-plane homogeneous field

We present a systematic theoretical study of the average in-plane magnetic field on square and rectangular magnetic field sensors from a single magnetic bead and a monolayer of magnetic beads magnetized by an in-plane externally applied homogeneous magnetic field. General theoretical expressions are derived such that the sensor response and its dependence on the sensor size, spacer layer thickness, bead diameter, and bead susceptibility can easily be evaluated. The average magnetic field from a single bead close to the sensor shows a strong dependence on the position of the bead and a change of sign when the bead passes the edge of the sensor in the direction of the applied field. Analytical approximations are derived for the average field from a homogeneous monolayer of beads for beads much smaller than the sensor dimension and for a bead size chosen to minimize the position sensitivity of the sensor response. We discuss implications for the sensor design and give general guidelines for optimum choices of sensor dimension, spacer layer thickness, and bead diameter, as well as simple expressions for the average magnetic field from the beads. The usage of the general guidelines is exemplified in the design considerations for a sensor, which is fully covered by 100 beads and has a spacer layer thickness of 100 nm.

구형파 2-Hall Sensor를 이용한 영구자석형 동기전동기의 벡터 제어

This paper proposes a new vector control method using two rectangular hall sensors instead of using the expensive encoder and resolver. The proposed method estimates the speed and motor position by using the quadruple of two hall sensors signals instead of encoder signal. The proposed new speed estimation method is stable under the rated speed range. This algorithm will be able to moderate prices of the whole system and apply to the condition unfitted with encoder and resolver.

Hybrid and module designs for ATLAS silicon tracker upgrade for super LHC

Based on the ATLAS SCT experience, hybrid and module designs of a short strip silicon detector for an upgraded ATLAS inner tracker for the super LHC have been pursued. At the super LHC, which provides 10 times more intense beam collisions than the LHC, the detectors envisage a very high rate operation in a much harsher radiation environment. Immediate concern is an increase of leakage current due to a radiation damage, which may induce a catastrophic break down of a thermal runaway. We have deduced a simple model for the thermal runaway, which can be conveniently utilized for the module designs. The thermal runaway model was verified by comparing with the corresponding FEM thermal analyses. The upgraded module is structurally similar to the present SCT barrel module. Two rectangular sensors, each of 12.5 × 6.4 cm 2 , are sandwiched along with a thermo-mechanical baseboard to provide two-dimensional space points. A one-piece wrap-around hybrid bridged over the sensors serves both the top and bottom sensors. Mounting and cooling schemes also follow the present barrel SCT designs with necessary modifications and improvements.

The response of rectangular piezoelectric sensors to Rayleigh and Lamb ultrasonic waves

A fundamental understanding of the response of piezoelectric transducer patches to ultrasonic waves is of increasing interest to the field of structural health monitoring. While analytical solutions exist on the interaction of a piezoelectric actuator with the generated Lamb waves, the behavior of a piezoelectric sensor has only been examined for the limited case of a piezo-actuated Lamb wave in a pitch-catch configuration. This paper focuses on the fundamental response of surface-bonded piezoelectric sensors to ultrasonic waves. The response to both Rayleigh waves and Lamb waves is examined, starting with harmonic excitation fields and moving to broadband and narrowband excitation fields. General oblique incidence of the wave on rectangular sensors is treated first; parallel incidence is then derived as a particular case. The solutions are developed analytically for the harmonic and the narrowband excitations, and semianalytically for the broadband excitation. The results obtained can be used to design ultrasonic sensors that are either particularly sensitive to a given mode or possess unique directivity behavior which, in turn, can greatly simplify current algorithms for damage detection and localization.

Quartz crystal microbalance sensor design: I. Experimental study of sensor response and performance

This paper investigates a novel quartz crystal microbalance (QCM) biosensor with a small and rectangular flow cell along with a correspondingly shaped crystal electrode. The sensor was evaluated with impedance analysis and compared to standard circular sensor crystals and sensor crystals with small circular electrodes. Comparative QCM measurements on an antibody–antigen interaction system were carried out on the rectangular and standard circular sensor systems. Impedance analysis and subsequent data extraction of the three different sensor crystals showed that the smaller sensors had significantly higher Q-values in air, but that liquid load on the electrodes lowered the Q-values radically for all crystals. Under liquid load, Q-values for the standard circular and the rectangular sensors were similar whereas the Q-value for the small circular sensor was 50% higher. QCM experiments showed that the QCM system with rectangular crystal electrodes was fully functional in a liquid environment. The rectangular system showed higher and more rapid responses for series of antibody injections, albeit at a higher noise level than the standard system. The study elucidates a significant potential for improvement of sensor performance by optimising the sensor electrode size and shape together with the flow cell geometry.

Selection of the Magnetic Circuit Design for Electromagnetic Fluid Flow Converter with Rectangular Channel

Technological advantages are the main cause of popularity of electromagnetic fluid flow converters with cylindrical channel. But electrode signal of electromagnetic fluid flow converters with rectangular channel sensors has the significantly lower dependence on a velocity profile in the cross-section of the channel. Sensitivity of electromagnetic fluid flow converters with rectangular channel is higher. It is showed, that using the same magnetic field excitation coils with the same current, the electromagnetic flow converters with rectangular channel has more than 1.5 times sensitivity, than the electromagnetic flow transducers with cylindrical channel. The sensitivity increases, when ratio between high and base of channel rectangular cross-section decreases. There are better to use rectangular magnetic core in the electromagnetic flow converters with rectangular channel, directing the longer side of core cross-section perpendicularly to channel axis. The magnetic material, needed for core manufacturing, can be diminished till two times comparing with cylindrical core in this case, when the magnetomotive force is the same. By simulation, using finite element method, the magnetic cores of rectangular and circular shapes were compared in the electromagnetic flow converters with perpendicular channel. In the flow transducers with rectangular core shape the sensitivity dependence on velocity profile is significantly lower. Using core of perpendicular shape with longer side 2.33 times more than shorter side in the range of average velocity 0-8m/s the variation of sensitivity is not exceeded of limits [-0.28%, 0.31%]. Using core of perpendicular shape with longer side 1.66 times more than shorter side in the range of average velocity 2-8m/s the variation of sensitivity is not exceeded of limits ±0.03%. By widening the electrodes, the variation of sensitivity can be diminished in the range of average velocity 0-8m/s. Ill.3, bibl.3 (in English; summaries in English, Russian and Lithuanian).

Capacitive pressure sensors and switches fabricated using strain compensated SiGeB

The fabrication of capacitive pressure sensors and pressure switches using a 2.4 μm thick strain compensated heavily boron doped SiGeB diaphragm is presented. The process relies on the silicon fusion bonding of two silicon wafers to seal the pressure sensor cavity and construct the device. Both rectangular and circular type pressure sensors and pressure switches have successfully been fabricated using this process. Results are presented of a capacitive type sensor operating in the medical pressure regime (0–300 mmHg) with a sensitivity to pressure of 1.5 fF/mmHg or 305 ppm/mmHg, and of a pressure switch operating in the 3–8 bar pressure range and are thus suitable for a number of industrial and automotive applications. The current flowing through the switch when biased at 2 V jumps over six orders of magnitude when its two plates come in contact at a well defined pressure threshold.

Influence of the electrodes configuration on a differential capacitive rain sensor performances

The dimensioning and experimental tests of a differential capacitive rain sensor without sensitive layer are presented. The detection principle relies on the change in electric permittivity induced by water on the active area of the sensor. This sensor is made of three protected coplanar electrodes defining two capacitors: a sensitive capacitor which capacitance ( C 1) varies with water, and an insensitive-reference-capacitor ( C 2). In dry condition, both capacitances have the same value. Imbalance between C 1 and C 2 reveals the presence of water on the sensor. Two types of electrodes are studied: rectangular and interdigital. The sensors geometrical configurations are first refined by numerical simulation using a finite element method (FEM). The sensors behavior in different rain conditions is then simulated using the same FEM software. Finally, sensors prototypes are manufactured and tested. The rectangular electrodes sensor exhibits a significant sensitivity to water due to both a maximum variation of the sensitive capacitance and a negligible variation of the reference capacitance, while the interdigital electrodes sensor appears to be less sensitive.

Development of a Palpation Sensor for Detecting Prostatic Cancer and Hypertrophy. Optimum Structural Design of Sensor.

This paper is concerned with the development of a palpation sensor for detecting the prostatic cancer and hypertrophy. The sensor is a layered medium with two polyvinylidene fluoride (PVDF) films embedded in the matrix rubber block. The temporal mean values, I1 and I2, of absolute voltage signals from the polymer films are calculated and their ratio I1/I2 is used as the sensor output. First, the fundamental characteristics of sensor are examined on a rectangular sensor with a plane surface. Then, the surface geometry of sensor is designed so that the sensor output clearly extracts the features on the stiffness of the materials. Finally, a compact cylindrical sensor which is inset in the doctor's forefinger is presented and its characteristics as a palpation sensor are studied experimentally. Some representative clinical data on the hardened and normal prostate glands are also presented.

Development of a palpation sensor for detection of prostatic cancer and hypertrophy (optimum structural design of sensor)

This paper is concerned with the development of a soft palpation sensor for detection of prostatic cancer and hypertrophy. The sensor is a layered medium with two polyvinylidene fluoride (PVDF) films embedded in the matrix sponge rubber. It is pressed against the prostates and the output voltage signals from the polymer films are measured. The temporal mean values, I1 and I2, of absolute voltage signals from the films are calculated and their ratioI1=I2 is used as the sensor output. First, the fundamental characteristics of a rectangular sensor with a plane surface are examined. Then, the surface geometry of the sensor was designed so that it clearly indicates the nature on the stiffness of the soft material. Finally, a compact cylindrical sensor attached to the doctor's forefinger is described and experimental studies of its performance as a palpation sensor are presented. Some representative clinical data on the normal and hardened prostate glands are also presented.

NEAR-FIELD MICROWAVE NONDESTRUCTIVE DISTINCTION BETWEEN SURFACE HEIGHT VARIATIONS AND DEFECTS IN THICK SANDWICH COMPOSITES USING STANDOFF DISTANCE OPTIMIZATION

Nondestructive inspection of thick composite materials is important for maintaining manufacturing quality and structural integrity. Microwave nondestructive inspection methods are well suited for inspecting such structures, and offer many advantages compared to other nondestructive inspecting approaches. Optimization of microwave measurement parameters offers great versatility in detecting various sub-surface and surface defects while providing a high level of detection robustness. For this study two different thick composite specimens were used, one with a disbond (due to an embedded mylar sheet) having also generated some level of surface height variation in the specimen and the other subjected to an impact damage. An open-ended rectangular waveguide sensor was used to detect and distinguish between the defects and the surface height they may have produced in the specimens. With this probe suspended above the specimen and at a fixed operating frequency, the standoff distance was optimized for detection of the sub-surface defect (the mylar sheet) while nulling out the effect of surface height variations and the impact damage (and vice-versa). Microwave images of sample areas were produced for these optimization exercises effectively showing the surface height variations or the presence of the mylar sheet, respectively. A similar approach was employed to detect the surface height depression caused as a result of the impact damage on the second specimen. The result show that the choice of standoff distance can be optimally used to look for a surface or sub-surface defect while eliminating any influence due to specimen surface height variations (and vice-versa).

REMOTE DETECTION OF SURFACE CRACKS/ SLOTS USING OPEN-ENDED RECTANGULAR WAVEGUIDE SENSORS: AN EXPERIMENTAL INVESTIGATION

Nondestructive surface crack detection is an important issue in many industrial, manufacturing and structural environments. Although there exist several standard nondestructive techniques, each possesses their respective advantages and disadvantages. Recent research activities in using open-ended microwave sensors has proved to be a viable practical approach. Microwave techniques offer many advantages including the fact that they may be used in a noncontact fashion while detecting exposed, filled and covered surface cracks. This paper explores the noncontact characteristics of employing an open-ended rectangular waveguide sensor at K-band. The results show the possibility of detecting thin and long machined slots/ cracks on aluminum plates at standoff distances of several millimeters. In addition, the results show that these cracks/ slots are readily detected when exposed, filled with rust and covered with several layers of common paint. A discussion of the findings is also presented.

Microwave Nondestructive Determination of Sand-to-Cement Ratio in Mortar

Abstract Microwave nondestructive testing methods have shown great promise for the inspection of cement-based materials. Previously it has been shown that the magnitude of reflection coefficient from cement paste specimens can be correlated to their water-to-cement (w/c) ratios and more importantly to their compressive strengths. For mortar specimens, the sand-to-cement (s/c) ratio plays an important role in its physical, mechanical, and microwave reflection properties. To determine the w/c ratio and other properties of mortar specimens, one also needs to know its s/c ratio. To illustrate the ability of microwave reflection measurements for this purpose, two sets of four mortar specimens are produced with w/c ratios of 0.50 and 0.60 and with s/c ratios of 1.0, 1.5, 2.0, and 2.5. The microwave reflection coefficients of these specimens are measured using an open-ended rectangular waveguide sensor, in the G- (3.95–5.85 GHz), J- (5.85–8.2 GHz), and X-band (8.2–12.4 GHz) frequency ranges. It is shown that a simple relationship between the standard deviation of the magnitude of the reflection coefficient of mortar and its s/c ratio exists, and a more sensitive relationship exists for higher frequencies (waveguide bands). This approach may be extended to nondestructively determine the aggregate volume content and size distribution in concrete specimens.

Microwave Nondestructive Determination of Sand-to-Cement Ratio in Mortar

Microwave nondestructive testing methods have shown great promise for the inspection of cement-based materials. Previously it has been shown that the magnitude of reflection coefficient from cement paste specimens can be correlated to their water-to-cement (w/c) ratios and more importantly to their compressive strengths. For mortar specimens, the sand-to-cement (s/c) ratio plays an important role in its physical, mechanical, and microwave reflection properties. To determine the w/c ratio and other properties of mortar specimens, one also needs to know its s/c ratio. To illustrate the ability of microwave reflection measurements for this purpose, two sets of four mortar specimens are produced with w/c ratios of 0.50 and 0.60 and with s/c ratios of 1.0, 1.5, 2.0, and 2.5. The microwave reflection coefficients of these specimens are measured using an open-ended rectangular waveguide sensor, in the G- (3.95–5.85 GHz), J- (5.85–8.2 GHz), and X-band (8.2–12.4 GHz) frequency ranges. It is shown that a simple relationship between the standard deviation of the magnitude of the reflection coefficient of mortar and its s/c ratio exists, and a more sensitive relationship exists for higher frequencies (waveguide bands). This approach may be extended to nondestructively determine the aggregate volume content and size distribution in concrete specimens.

Microwave Detection of Rust Under Paint and Composite Laminates

Accurate, reliable, and early detection of rust/corrosion under paint and laminate composites in many industrial and military applications is of great concern and interest. Although there are several methods for detecting rust under paint, they all have their respective limitations. Microwave nondestructive and noncontact inspection techniques are well suited for the early and reliable detection of rust under various paints and composite laminates. In this paper, the potential of utilizing open-ended rectangular waveguide sensors for detecting rust under paint and laminate composites is investigated theoretically and experimentally. An electromagnetic model describing the interaction of microwave signals radiating from an open-ended rectangular waveguide with a stratified dielectric structure is used to model the presence of rust under paint and a composite laminate coating. For the experimental investigations, we used a rusted steel specimen that was painted over by common spray paint to as much as ten coats of paint. These experiments are conducted at 24 and 10 GHz. The issue of detecting rust unambiguously while a certain paint thickness variation may exist is also addressed.

Microwave Detection of Rust Under Paint and Composite Laminates

Abstract Accurate, reliable, and early detection of rust/corrosion under paint and laminate composites in many industrial and military applications is of great concern and interest. Although there are several methods for detecting rust under paint, they all have their respective limitations. Microwave nondestructive and noncontact inspection techniques are well suited for the early and reliable detection of rust under various paints and composite laminates. In this paper, the potential of utilizing open-ended rectangular waveguide sensors for detecting rust under paint and laminate composites is investigated theoretically and experimentally. An electromagnetic model describing the interaction of microwave signals radiating from an open-ended rectangular waveguide with a stratified dielectric structure is used to model the presence of rust under paint and a composite laminate coating. For the experimental investigations, we used a rusted steel specimen that was painted over by common spray paint to as much as ten coats of paint. These experiments are conducted at 24 and 10 GHz. The issue of detecting rust unambiguously while a certain paint thickness variation may exist is also addressed.

Visible spectroscopy in the DIII–D divertor

Spectroscopy measurements in the DIII–D divertor have been carried out with a survey spectrometer that provides simultaneous registration of the visible spectrum over the region 400–900 nm with a resolution of 0.25 nm. Broad spectral coverage is achieved through the use of a fiberoptic transformer assembly to map the curved focal plane of a fast (f/3) Rowland-circle spectrograph [Tugarinov et al., Rev. Sci. Instrum. 66, 603 (1995)] into a rastered format on the rectangular sensor area of a two-dimensional charge-coupled device (CCD) camera. Vertical grouping of pixels during CCD readout integrates the signal intensity over the height of each spectral segment in the rastered image, minimizing readout time. For the full visible spectrum, readout time is 50 ms. Faster response time (<10 ms) may be obtained by selecting for readout just a small number of the 20 spectral segments in the image on the CCD. Simultaneous recording of low charge states of carbon, oxygen, and injected impurities has yielded information about gas recycling and impurity behavior at the divertor strike points. Transport of lithium to the divertor region during lithium pellet injection has been studied, as well as cumulative deposition of lithium on the divertor targets from pellet injection over many successive discharges.

Microwave detection and depth determination of disbonds in low-permittivity and low-loss thick sandwich composites

Nondestructive evaluation (NDE) of disbonded low-permittivity and low-loss dielectric multilayered composite media is of considerable interest in many applications. The ability of microwaves to penetrate inside dielectric materials makes microwave NDE techniques very suitable for interrogating structures made of multilayered dielectric composites. Additionally, the sensitivity of microwaves to the presence of dissimilar layers in such materials allows for accurate detection of a disbonded layer. In a multilayered composite, a disbond may occur between any two (or more) layers. The potential of utilizing microwave NDE techniques for the detection and depth estimation of disbonds in a thick sandwich composite is investigated. This study utilizes a theoretical model developed for investigating the interaction of microwave radiation from an open-ended rectangular waveguide sensor with ann-layer dielectric composite medium. The influence of the standoff distance between the sensor and the medium and the operating frequency on the sensitivity of disbond detection and depth estimation is studied to obtain an optimum set of parameters for enhanced detection sensitivity. Results of the theoretical study are presented with a discussion on the optimization process for a thick sandwich composite composed of 13 dielectric layers.

Pressure distribution and perceived comfort in casual footwear

The aim of this investigation was to establish the relationship between short-term perceived comfort and pressure distribution on the dorsal and plantar surfaces of the foot, while walking in a range of commercially available casual footwear. The study was carried out in the biomechanics laboratory of Manchester Metropolitan University using 15 male subjects without foot pathology. Perceived upper and plantar comfort were measured using a specially designed questionnaire, while dorsal and plantar pressure distributions were measured using a rectangular sensor pad recording at 30 Hz and a Mikro-EMED insole recording at 100 Hz respectively. Analysis of variance tests were used to determine differences in perceived comfort and pressure distribution between three pairs of shoes. The findings of this study suggest that an increase in total plantar force and force-time integral may relate to a decrease in perceived plantar comfort. For the three shoes examined in this study, overall peak plantar pressure, the pressure-time integral, and total plantar area did not appear to be linked to perceived plantar comfort. Findings for the shoe upper indicate that decreased dorsal forces and pressures may be related to decreased upper comfort. These findings suggest that the measurement of pressure distribution at the foot-shoe interface could be a useful tool in identifying the causes of discomfort in footwear.

Approximate evaluation of the spectral density integral for a large planar array of rectangular sensors excited by turbulent flowa)

An approximate numerical procedure has been developed for rapidly evaluating the spectral density integral that predicts the output of a planar array of many sensors excited by turbulent boundary layer pressure fluctuations. This procedure is particularly useful in cases where the transfer function factor of the integrand is not a simple function of the wave numbers in the flow and transverse directions. The procedure exploits the facts that the entire integrand is a separable function of these two wave numbers and, when the number of sensors is large, the array function factor of the integrand is a rapidly varying function of wave number, characterized by many similar shaped lobes. In addition, a model for multilayered media is employed to provide the transfer function for boundary conditions that closely correspond to reality. Results generated by this procedure were compared to those from an exact evaluation of the integral which is possible if the transfer function is taken to be constant; there was agreement to within 0.2 dB or better over a broad frequency interval. Some results for a realistic transfer function are presented, such as the case of an elastomeric layer backed by an elastic plate with the sensors embedded at an arbitrary position within the layer.