Cylindrical Sensor Research Articles

Cylindrical sensor geometry for absorbance-based fiber-optic ammonia sensors

A novel cylindrical shape geometry is proposed for fiber-optic ammonia sensors based on chromophoric indicator dyes. Sensors are constructed by trapping the internal indicator solution inside a short segment of a gas-permeable tube. Fiber-optic probes are used to supply incident radiation and to collect light that transverses through the internal solution. This cylindrical sensor geometry provides large optical path lengths which permits the use of chromophoric indicator dyes. Unlike the conventional distal tip geometry, the diffusion path is independent of the optical path which results in short response times coupled with high sensitivity and low limits of detection. Our experiments indicate that stray radiation is negligible for this sensor design, and that the optical path length essentially equals the distance between the fiber-optic probes. Sensors constructed with Bromothymol Blue as the indicator dye are evaluated. As part of this evaluation, three different modes of operation are tested. The best analytical performance obtained when a single discrete aliquot of the internal solution is used. Steady-state responses are achieved within 13–16 min for 200 n M levels of ammonia from sensors with limits of detection ranging from 150 to 20 n M.

A liquid level sensor using the absorption of guided acoustic waves

This liquid level sensor consists of a vertically movable 10-cm-long hollow cylinder with an impedance matching conic section suspended at one end of a few-meters-long magnetorestrictive wire. The wire is automatically wound up or unwound such that the cylindrical sensor element at the bottom of the wire is immersed by just a small and measurable distance into the liquid whose level is sought. Acoustic waves are launched in the wire by a pulse of current in a coil and are transmitted to the hollow cylinder through the cylindrical horn. The carrier frequency of the wave trains and the thickness of the tube are chosen so that the elastic waves strongly leak into the liquid when the hollow cylinder is immersed. The level is then determined by measuring the time-of-flight of the echo reflected at the junction between the wire and the horn, followed by taking into account a small correction term computed from the attenuation of the end echo.

Determining the axis of a surface of revolution using tactile sensing

Dextrous robot hands need to be able to determine the pose of objects to reliably grasp and manipulate them. The first contacts with an object can be used to provide an initial estimate of this information if the object is constrained to be of a particular class. The authors consider a simple example of exploiting class constraints: finding the axis of an unknown surface of revolution. Three tactile curvature measurements on a surface of revolution with twice-differentiable sweeping rule function are shown to be sufficient for determining the axis except for certain singular configurations. Position and orientation error uncertainties and experimental results are presented for a cylindrical tactile sensor.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The theory of operation of piezoelectric quartz crystal sensors for biochemical application

Piezoelectric quartz crystal shear wave generators have long been employed as mass detectors using the Sauerbrey equation to relate observed changes in resonant frequency to changes in mass. When these crystals are used in a more sophisticated way to detect the binding of an analyte by means of a sensor layer attached to the crystal, there is often considerable discrepancy between the mass change determined and that expected from the reaction. We re-examine the operation of the device in terms of the underlying shear wave processes and show that the viscoelastic properties of the layers on the crystal, rather than the simple mass, determine the change in resonant frequency. The theory is illustrated by examples of X-cut cylindrical and AT-cut planar crystal sensors for saccharides, based on interaction with concanavalin-A bound on the crystals. The correct emphasis on viscoelastic shear wave properties rather than mass change offers much better prospects for the successful use of such devices as biosensors.

Development of a Thin Film Environmental Monitor

Abstract A device has been developed by researchers at the National Institute for Occupational Safety and Health (NIOSH) for real-time monitoring of exposure to airborne contaminants, including in-mask respirator sampling. The device consists of a small breathing-zone sensor connected to a belt-mounted unit. The cylindrical sensor, which weighs 15 g and is 2 cm in diameter and 2.5 cm long, contains a thin film of chemical reagent that changes color upon exposure to a particular contaminant, and an optical system that monitors the color change. The belt-mounted unit (450 grams) provides power to the sensor, pulls air through it, and processes its electrical output. The output signal is a function of the total contaminant exposure, can be processed to provide real-time concentration data, can be recorded, or can be used to trigger an audible alarm. Five prototype devices were constructed and their capability to monitor ammonia and mercury was investigated. Evaluation of this device using a commercially-proc...

Using a cylindrical tactile sensor for determining curvature

It is shown how contact curvature can be determined from a single contact with a cylindrical tactile sensor. When the tactile finger touches an unknown smooth convex surface, contact location, principal curvatures, and normal force are determined from a 4*4 window of strain measurements. Contact properties are determined by a nonlinear model-based inversion from strain measurements back to the contact type. Sensor strains are predicted by convolving the spatial impulse response of the rubber skin with the assumed surface pressure distribution derived from a Hertz contact model. Gradient search finds the parameters of the convex second-order shape and the force that best fit the sensor data. Experiments under laboratory conditions show radius estimation within 10%, orientation within 3%, and subtactel (tactile element) localization to 3% of the element spacing. Using a linearized model, error bounds due to sensor noise on the inversion process are predicted.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Tactile Sensing Mechanisms

This paper has three main themes: design of a cylindrical tactile sensor, mechanical analysis using planar linear elas ticity models, and signal analysis for determining basic infor mation about the applied contact. An analysis of appropriate sensor depth has been used to allow accurate localization of contacts and reduced spatial aliasing. A comparison has been made between the cylindrical sensor and a simple two- dimensional stress-strain model. The effects of skin thickness and sensor depth on sensitivity are analyzed. Preliminary methods for determining contact location, total force, and tangential force with only normal deflection sensors have been implemented for a line contact.

Eddy current methods for evaluation of the transformed fraction of metals by voltage source

Finite-element methods employing voltage sources rather than widely used current sources are used to evaluate magnetic permeability, impedance, and transformed fraction in metals. The transformed fractions have been successfully estimated by nondestructive eddy-current measurements using voltage sources. The experimental results agree well with those of numerical simulations. The authors also investigate the sensitivity of the eddy-current measuring system as a function of the various parameters by numerical simulations, and present a suitable measuring environment for nondestructive testing of the properties of materials. It is determined that a rectangular sensor may be better than a cylindrical sensor in eddy-current measurements of conductive material.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Polymer-coated cylindrical waveguide absorption sensor for high acidities

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolymer-coated cylindrical waveguide absorption sensor for high aciditiesW. Patrick. Carey, Michael D. DeGrandpre, and Betty S. JorgensenCite this: Anal. Chem. 1989, 61, 15, 1674–1678Publication Date (Print):August 1, 1989Publication History Published online1 May 2002Published inissue 1 August 1989https://doi.org/10.1021/ac00190a018RIGHTS & PERMISSIONSArticle Views112Altmetric-Citations30LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (650 KB) Get e-Alerts Get e-Alerts

Three-dimensional flux-sensor composed of high-T/sub c/ superconductor

A three-dimensional flux sensor has been studied with the aim of realizing a practical application of high-T/sub c/ oxide superconductor Y-Ba-Cu-O. Thick-film and cylindrical sensors were made and examined. The current-voltage characteristics were investigated as a function of magnetic field at liquid nitrogen temperature. The flux flow was observed in a wide range of magnetic fields from 0.001 to 1 Tesla, and the magnetic field could be evaluated by the output voltage. The dependence of the voltage on the angle between the current and magnetic field direction was also examined. The flux flow was affected by the direction of the external magnetic field, resulting in a change of the output voltage. The output voltage was found to show hysteresis with respect to the external field. On the basis of these phenomena, a three-dimensional flux sensor was designed and fabricated. >

Measurement of velocity vectors with orthogonal and non-orthogonal triple-sensor probes

A new method of interpreting the signals from triple-sensor thermal anemometer probes has been developed based on fast solution for all the roots of the non-linear Jorgensen (1971) equations describing the directional response of each cylindrical sensor. The sensors can be oriented at arbitrary angles to each other, but always within a range of probe geometries that keep prong interference and thermal wake interference below acceptable levels. The properties of a class of non-orthogonal symmetric tetrahedral probe geometries are studied in relation to the range of flow vector angles that can be measured, the sensitivity of the probe with respect to changes in flow angle, and the sensitivity of the computed velocity components due to angular errors associated with the construction of the probe. The solutions of Jorgensen's equations are inherently multiple-valued, but if the velocity vector is restricted to be within a cone of angles, they are unique. It is shown that measurements with non-orthogonal triple sensor signals are sensitive to angular deviations of a few degrees of the sensor angles from the nominally orthogonal probe geometry, indicating the need of a non-orthogonal algorithm. The mean, rms, Reynolds stress, and power spectrum of the velocity in fully developed turbulent pipe flow were measured using a specially designed triple sensor probe and the proposed algorithm.

A comparison of cylindrical and flat plate sensors for surface wetness duration

Cylindrical surface wetness duration sensors were constructed and tested for use in onions. Their potential for use as wetness sensors in flat-leaved crops was also investigated. Dew deposition on both cylinders and flat plates was shown to depend on sensor size, while drying of simulated raindrops depended on drop size. Despite these similarities, dew typically fell 1–2 h earlier and lasted 2–3 h longer on flat plates than on cylinders of the same size. Drops evaporated faster on cylinders than on flat plates at wind speeds < 1.5 m s −1, but similar rates of drying were observed for drops on both sensor shapes at higher wind speeds.

Directional Sensitivity of Cylindrical Hot-Film Velocity Sensors

Directional sensitivities of alumina and quartz-coated cylindrical hot-film velocity sensors with ls/ds ratios near 20 were investigated in air and liquid Refrigerant-113 flows. The well-known effective cooling velocity relation Ueff2(α) = U2(0)[cos2α+k2sin2α] represents the experimental data well. Values for the parameter k as well as heat transfer relations are presented.

Heat transfer for the cylindrical film sensor of a thermal anemometer

The authors investigate heat transfer for the cylindrical film sensor of a thermal anemometer.

Evaluation of Transesophageal Doppler Detection of Air Embolism in Dogs

The authors assessed the use of a cylindrical sensor which transceives (transmits and receives) ultrasound in a 360 degree arc mounted on a standard esophageal stethoscope catheter to detect air embolism in dogs. They used electronic circuitry developed specifically to provide a continuous analog recording of high frequency Doppler energy as well as an audible signal. They found that the esophageal Doppler sensor was easy to position. In 25 of 30 dogs, the system distinguished Doppler sounds of venous air emboli that were present either in the superior vena cava, right atrium, right ventricle, or pulmonary artery from normal cardiovascular sounds. In the remaining five animals, Doppler heart and air emboli sounds were initially of poor quality, but improved with aspiration of air from the esophagus. In another five dogs, arterial air emboli produced by left ventricular injections also were detected. The esophageal sensor was sensitive to both venous and arterial air emboli ranging from 0.05--0.2 ml of air, and the authors consistently detected repeated intravenous injections of air throughout a 5-h time period. Optimal position of the sensor for detection of venous air emboli was at the level of the superior vena cava above its junction with the right atrium. Optimal position to detect arterial air emboli introduced via a left ventricular catheter was at the level of the aortic arch. Tissue analysis of the esophagus revealed no morphologic damage due to the sensor or transmitted energy.

A note on the measurement of transverse velocity fluctuations with heated cylindrical sensors at small mean velocities

The measurement of transverse velocity fluctuations and Reynolds stresses with heated cylindrical sensors is studied at low mean velocities, 0.5 m s-1<U<10 m s-1, using a dynamic technique. It is concluded that the yaw sensitivity has a significant dependence upon the mean velocity within this range. The results indicate that there may be considerable difficulty in obtaining accurate turbulence measurements in large meteorological wind tunnels run at the low velocities.

Evaluation of transesophageal Doppler detection of air embolism in dogs.

The authors assessed the use of a cylindrical sensor which transceives (transmits and receives) ultrasound in a 360 degree arc mounted on a standard esophageal stethoscope catheter to detect air embolism in dogs. They used electronic circuitry developed specifically to provide a continuous analog recording of high frequency Doppler energy as well as an audible signal. They found that the esophageal Doppler sensor was easy to position. In 25 of 30 dogs, the system distinguished Doppler sounds of venous air emboli that were present either in the superior vena cava, right atrium, right ventricle, or pulmonary artery from normal cardiovascular sounds. In the remaining five animals, Doppler heart and air emboli sounds were initially of poor quality, but improved with aspiration of air from the esophagus. In another five dogs, arterial air emboli produced by left ventricular injections also were detected. The esophageal sensor was sensitive to both venous and arterial air emboli ranging from 0.05--0.2 ml of air, and the authors consistently detected repeated intravenous injections of air throughout a 5-h time period. Optimal position of the sensor for detection of venous air emboli was at the level of the superior vena cava above its junction with the right atrium. Optimal position to detect arterial air emboli introduced via a left ventricular catheter was at the level of the aortic arch. Tissue analysis of the esophagus revealed no morphologic damage due to the sensor or transmitted energy.

CMICE: A near-surface current meter intercomparison experiment

A moored Current Meter Intercomparison Experiment called CMICE was conducted 6 km off the southern coast of Long Island, New York near 40°47′N, 72°30′W during February and March 1976. A total of 20 current meters were deployed on six moorings set in a linear array parallel to the local coastline and topography. The seven instrument types used were the Aanderaa RCM-4, the AMF VACM, the Brookhaven National Laboratory spar buoy system with cylindrical and spherical Marsh-McBirney electromagnetic sensors, the EG&G 850 and CT-3, and the Chesapeake Bay Institute modified ENDECO 105. Current meters were grouped at four depth levels (3.5, 7.4, 15.7, and 25.0 m). Water depth was 27.8 m. Wave data were obtained at the site and 10-m wind data were recorded at the coast 7 km north. Intercomparison of 1 h vector-averaged velocities from instruments of the same type at the same level in the array indicated sufficient horizontal flow homogeneity to allow evaluation of instrument-mooring differences. For properly operating meters the general agreement was typically within ±5 cm s −1 in speed and ±5° in direction for wave heights from 0 to 3.5 m and wave periods from 5 to 9 s. Analysis of instrument and mooring performances shows significant differences in response to surface wave and mooring motion.

Hot-film anemometry in aqueous NaCl solutions

An experimental investigation was performed on the calibration of cylindrical hot-film sensors in aqueous NaCl solutions. The results are consistent with Kramers' law provided the Reynolds number exponent is reduced to 0.36 and correction is made for conduction to the quartz fiber backing. A modified King's law appears to provide a useful approximation to the usual Kramers' law for practical applications of hot-film sensors in flows of variable density. The modified King's law provides a simple method for estimating the magnitude of errors introduced when variable density effects are ignored in the velocity calibration of a hot-film sensor in saline solutions.

A comparative study of the signal-to-noise ratio for hot-film and hot-wire anemometers

The signal-to-noise ratio of a constant-temperature anemometer with a cylindrical hot-film sensor is compared with the signal-to-noise ratio of a hot-wire anemometer. It is found that for equivalent operating conditions a typical hot-film anemometer has a lower signal-to-noise ratio than a typical hot-wire anemometer. The situation can be improved by designing for a drastic increase in the film resistance and by selecting a film material with a high temperature coefficient of resistivity.