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Showing papers in "Measurement Science and Technology in 1994"


Journal ArticleDOI
TL;DR: In this article, a sensitivity analysis of the two-colour pyrometry technique for calculation of soot temperature T and volume fraction fv is presented, taking into account particle shape, different expressions for monochromatic emissivity, optical property variations, size distribution of the soot particles and a finite light-detection bandwidth.
Abstract: A sensitivity analysis of the two-colour pyrometry technique for calculation of soot temperature T and volume fraction fv is presented. Two different combustion environments are exemplified for high (fv approximately=10-5) and low (fv approximately=10-7) soot concentration regimes. The calculations are carried out taking into account particle shape, different expressions for monochromatic emissivity, optical property variations, size distribution of soot particles and a finite light-detection bandwidth. The results indicate which spectral range, for the choice of the ( lambda 1, lambda 2) wavelengths employed in the emission measurements, and computing algorithm, for the reckoning of the T values, can be appropriated to guarantee a lower a priori uncertainty in the T and fv calculated values. Results stress the evidence that T and fv values are critically sensitive to the complex refractive index, m=n-ik, and that they are irrelevantly influenced by the probability distribution of particle size. The critical theoretical influence of the type of fuel, characterized by a different soot hydrogen/carbon ratio, upon the inferred fv values is assessed. Determinations of temperature values with ( lambda 1, lambda 2) measurement wavelengths above 1.2 mu m is demonstrated to be invalidated by an uncertainty contribution of at least 20 K in the regime fv approximately=10-5 and 100 K in the regime fv approximately=10-7.

96 citations


Journal ArticleDOI
TL;DR: In this article, two phase extraction algorithms, in which step sizes need not be known or equal, are described, and a previously published algorithm is used for the final phase calculation.
Abstract: Two novel phase extraction algorithms, in which step sizes need not be known or equal, are described. One algorithm requires a minimum of five interferograms from which intensity offset and intensity modulation are calculated at each pixel and the relative phase is calculated for all pixels with respect to a reference pixel. The other algorithm requires two phase stepping mechanisms and a minimum of ten interferograms. The intensity characteristics and reference phase step are calculated at each pixel and a previously published algorithm is used for the final phase calculation.

85 citations


Journal ArticleDOI
TL;DR: In this paper, a torque magnetometer was designed for measuring standard sized rock samples, and two hinges of crossed leaf-springs were employed to integrate a stepper motor in the sample holder for the rotation of the specimen in the external magnetic field.
Abstract: A highly automated torque magnetometer has been designed, mainly for measuring standard sized rock samples. By employing two hinges of crossed leaf-springs it was possible to integrate a stepper motor in the sample holder for the rotation of the specimen in the external magnetic field. The dynamic range of the instrument covers the torque signals of most rock types. Additionally the instrument is able to measure the magnetocrystalline anisotropy of monocrystals.

83 citations


Journal ArticleDOI
TL;DR: A review of recent progress made in a range of selected fibre-optic sensors for physical measurands is presented, with particular attention paid to new developments, which have the potential to be exploited in a variety of wide applications as discussed by the authors.
Abstract: A review of recent progress made in a range of selected fibre-optic sensors for physical measurands is presented, with particular attention paid to new developments, which have the potential to be exploited in a variety of wide applications.

74 citations


Journal ArticleDOI
TL;DR: In this article, a capacitance-based tomography system for interface imaging inside a separator has been developed and tested in the separator laboratory at Christian Michelsen Research (CMR).
Abstract: Optimal quality of the product that leaves a water/oil/gas separator is determined by optimal separator design and control. Current control strategies for separators are extremely simple due to the lack of a reliable interface level measurement system. In this project a capacitance-based tomography system for interface imaging inside a separator has been developed and tested in the separator laboratory at Christian Michelsen Research (CMR). The tomography system consists of a capacitance sensor system, a data acquisition system and a model-based reconstruction algorithm implemented on a personal computer. The system can potentially measure the water, oil/water emulsion, oil and foam heights inside a separator on a process plant. In this project the tomograph has been tested, in a separator laboratory at CMR, for on-line imaging of water, oil and air interface levels (during water/oil/air tests) and for oil, foam and air interface imaging (during oil/air tests). The obtained accuracy is within 1.0 cm for all phases. The tomograph also detected the presence of foam, but due to problems with electrostatic charge generation, poor stability in the measurements results. In a steel separator, however, it is expected that the electrostatic charge problem will probably not exist.

71 citations


Journal ArticleDOI
TL;DR: In this paper, a multi-interface level measurement system using a 64-segment capacitance sensor has been developed for use in oil separators, which can not only locate the multi-interfaces between different phases, such as gas/oil, oil/water and water/sludge, but also detect the foam layer between gas and oil.
Abstract: A multi-interface level measurement system using a 64-segment capacitance sensor has been developed for use in oil separators. It can not only locate the multi-interfaces between different phases, such as gas/oil, oil/water and water/sludge, but also detect the foam layer between gas and oil. Experimental results show that the interfaces of gas/oil and oil/water can be easily identified by using a simple normalized difference algorithm and the foam signal has a unique spectrum that can be acquired by fast Fourier transform analysis.

63 citations


Journal ArticleDOI
TL;DR: In this paper, the main magnetomechanical properties of magnetically soft, amorphous alloys of Fe, Co and Ni, in the three forms generally available: ribbons typically 20-50 mu m thick and 1-25 mm wide; wires typically 30-130 mu m in diameter; and films 0.01-10 mu m thickness, deposited on substrates 25-250 mu m thin.
Abstract: Amorphous materials in the form of ribbons, wires and thin films require special care to be taken in measurements of magnetostriction, the field dependence of elastic moduli and the magnetomechanical coupling factor. Problems arise in these measurements because of the sample geometry and, in some cases, because of the low anisotropy commonly found in amorphous ferromagnetic materials. This paper describes the methods that have been adapted or designed to measure the main magnetomechanical properties of magnetically soft, amorphous alloys of Fe, Co and Ni, in the three forms generally available: ribbons typically 20-50 mu m thick and 1-25 mm wide; wires typically 30-130 mu m in diameter; and films 0.01-10 mu m thick, deposited on substrates 25-250 mu m thick. The methods are described in sufficient detail, supported by numerous references, to enable readers to make a critical choice between them, taking into account such things as the temperature range, sensitivity and geometry. Magnetostriction measurements are classified as direct or indirect. The direct methods covered are the strain gauge, three-terminal and cantilever capacitance dilatometry, optical methods and the tunnelling tip method. Indirect methods include the small-angle magnetization rotation (SAMR) method, susceptibility measurements, the Wiedemann effect and strain-modulated ferromagnetic resonance (SMFMR). The methods described for measuring the field dependence of Young's modulus (the Delta E effect) and magnetomechanical coupling factor k are the resonance-antiresonance method, including the use of the impedance or admittance circle, the vibrating reed method and ultrasonic wave velocity methods. The use of a torsional pendulum for measuring the shear modulus and internal friction is also described.

59 citations


Journal ArticleDOI
TL;DR: In this article, a broad band ultrasonic relaxation spectrometer for liquid attenuation and velocity measurements below 1 MHz with one planar and one concave piezoelectric transducer is described.
Abstract: Ultrasonic resonator cells for liquid attenuation and velocity measurements below 1 MHz with one planar and one concave piezoelectric transducer are described. Such cells with a limited sample volume are needed for broad band ultrasonic relaxation spectrometry and for studies in chemical reaction kinetics, particularly for frequencies below 200 kHz. Measurement and evaluation procedures are described and an example of a broad band spectrum is shown.

59 citations


Journal ArticleDOI
TL;DR: In this paper, a tunable laser-atomic beam photoelectron source with sub-milli-electron-volt resolution, producing energy-variable free electrons (current 10-12 A) by resonant two-step laser photo-ionization of metastable Ar*(4s 3P2) atoms in a collimated beam, is described.
Abstract: A novel tunable laser-atomic beam photoelectron source with sub-milli-electron-volt resolution, producing energy-variable free electrons (current 10-12 A) by resonant two-step laser photo-ionization of metastable Ar*(4s 3P2) atoms in a collimated beam, is described. Operation and application of the source are demonstrated by a series of laser photoelectron attachment experiments, in which the process e-(E)+SF6 to SF6- is investigated in the electron energy range 0

55 citations


Journal ArticleDOI
TL;DR: In this paper, a measurement system consisting of two high-speed two-colour pyrometers is described; the system is suitable for monitoring the flattening and cooling of particles on a substrate during plasma spray deposition.
Abstract: A measurement system consisting of two high-speed two-colour pyrometers is described; the system is suitable for monitoring the flattening and cooling of particles on a substrate during plasma spray deposition. The first double-wavelength optical fibre pyrometer is focused 2 mm before the substrate and the other is focused on the substrate surface. The present instrument provides data on the temperature, the velocity and the size of a particle prior to its impact on a substrate and on its flattening and cooling when it impinges on the surface. Examples of results are given with plasma-sprayed zirconia particles impacting on bare steel substrates. Measurements are presented in terms of flattening time and 'apparent' degree of flattening as a function of the velocity, surface temperature and size of the impinging particles.

55 citations


Journal ArticleDOI
TL;DR: In this paper, a pulsed low-energy positron system for positron-lifetime spectroscopy has been up-graded and modified with regard to its three main components.
Abstract: A pulsed low-energy positron system for positron-lifetime spectroscopy has been up-graded and modified with regard to its three main components. A new moderator preparation chamber has been added, the radiofrequency pulsing concept has been modified using a pre-buncher and a pre-chopper in front of the existing chopper-buncher section. Furthermore, a new target station allowing measurements at variable temperatures has been incorporated. The lifetime spectra now reveal a strongly increased ratio of peak to background and of peak to satellite peak.

Journal ArticleDOI
TL;DR: Preliminary results on a test coil show acoustic noise attenuation behaviour consistent with theory and will significantly reduce the dangers to patients of high-level exposure to noise in medical resonance imaging scanners.
Abstract: A new technique for quiet gradient coil design in magnetic resonance imaging is proposed. Preliminary results on a test coil show acoustic noise attenuation behaviour consistent with theory. Active acoustic screening will significantly reduce the dangers to patients of high-level exposure to noise in medical resonance imaging scanners.

Journal ArticleDOI
TL;DR: In this article, a new interferometer was developed for absolute length measurement of length bars between 100 and 1500 mm in length, with an estimated uncertainty of length measurement (at 95% confidence level) of + or 30 nm+or 6.2*10-8 L, where L is the length of the bar.
Abstract: A new interferometer has been developed for absolute length measurement of length bars between 100 and 1500 mm in length. The interferometer uses a combination of three-wavelength interferometry and phase-stepping interferometry to measure the length, flatness and mutual parallelism of the measuring faces, and thermal expansion of the bars, with direct traceability to realizations of the metre and the kelvin. The interferometer is operated inside a sealed chamber to minimize the effects of refractive index variations. The design and operation of the interferometer are presented, with representative results of length, flatness and parallelism and thermal expansivity measurements. The instrument has an estimated uncertainty of length measurement (at 95% confidence level) of +or-30 nm+or-6.2*10-8 L, where L is the length of the bar.

Journal ArticleDOI
TL;DR: In this article, a linear critical-angle refractometer for liquids is described, where a 1728 element linear CCD array is used to scan the intensity profile of the output image, within which the position of a cutoff edge is a linear function of refractive index.
Abstract: A new version of the linear critical-angle refractometer for liquids is described: a 1728 element linear CCD array is used to scan the intensity profile of the output image, within which the position of a cut-off edge is a linear function of refractive index. The precision in locating this cut-off edge is greatly increased, especially for milky liquids, by differentiating the intensity profile numerically. Further information about complex particulate liquids is found to be given by the shape of the differentiated profile, and alternative internal and external illumination modes are provided which may give more information. The present instrument covers the refractive index range 1.3000 to 1.4700, with an accuracy of +or-0.0001 for transparent liquids. The light source is an LED at 635 nm. The intensity profile, the differentiated intensity profile, and the refractive index value are all computed, displayed and printed by a desk-top computer.

Journal ArticleDOI
TL;DR: In this article, an alternative operation mode of conventional, two-component phase Doppler anemometry systems is proposed, which removes these errors for many applications, and its improved performance is verified experimentally.
Abstract: The Gaussian beam defect is now a well documented deficiency of conventional phase Doppler anemometers and leads to significant errors in particle size estimation when the particle size takes on dimensions of the same order as the measurement volume. In the present paper, an alternative operation mode of conventional, two-component phase Doppler anemometry systems is proposed, which removes these errors for many applications. The new approach is analysed theoretically and its improved performance is verified experimentally. Furthermore, the effect of a slit aperture on the trajectory-dependent size measurement has been experimentally investigated.

Journal ArticleDOI
TL;DR: In this article, a passive vision-based sensor combines infrared imaging of the weld pool and selective optical filtering, both to reduce excessive arc glare and improve contrast between welding pool and heat affected zone (HAZ).
Abstract: The development of a novel sensor for the measurement of bead size in tungsten inert gas (TIG) welds is described. A passive vision-based sensor combines infrared imaging of the weld pool and selective optical filtering, both to reduce excessive arc glare and improve contrast between weld pool and heat affected zone (HAZ). The arc interruption and external illumination techniques, used by others, are not required. Image quality is shown to be comparable to that obtained with external illumination and superior to that of arc interruption methods. The technique has been successfully applied to both pulsed and continuous TIG welding of stainless steel in order to maintain the bead size during a welding run.

Journal ArticleDOI
TL;DR: In this article, the design, development and calibration of an impact force transducer or penetrometer, for use on the Huygens spacecraft scheduled to land on the surface of Saturn's satellite Titan, is described.
Abstract: The design, development and calibration of an impact force transducer or penetrometer, for use on the Huygens spacecraft scheduled to land on the surface of Saturn's satellite Titan, is described, The thumb-sized transducer employs a piezoelectric sensing element and is capable of working at cryogenic temperatures. Use of the sensor on a spacecraft imposes several reliability and safety constraints, as well as the desire to minimize mass (the sensor mass is 15 g). The impact force profile, measured at 10 kHz by the sensor, allows estimation of the density and cohesion of the surface material, and its particle size distribution. Sample profiles for terrestrial materials (sand, gravel and clay) are given.

Journal ArticleDOI
TL;DR: In this paper, a high-speed high-spatial-resolution pyrometer system for temperature measurement in a wide range of laser applications is illustrated by heat treatment, welding, cladding and alloying.
Abstract: The opportunities for temperature measurement by a high-speed high-spatial-resolution pyrometer system in a wide range of laser applications are illustrated by heat treatment, welding, cladding and alloying. Continuous CO2 and pulsed Nd:YAG laser machining are considered. The influence of such factors as beam traverse speed, laser power (or pulse energy), slab thickness, melt drop expulsion and distance from the seam centre on temperature evolution is analysed. The experimental results are analysed by numerical simulation.

Journal ArticleDOI
TL;DR: An improved version of a Marx bank circuit using 2N5551/2N5550 transistors as switching elements in avalanche mode was developed in this paper, which provides a negative pulse of about 4 kV amplitude and
Abstract: An improved version of a Marx bank circuit has been developed using 2N5551/2N5550 transistors as switching elements in avalanche mode which provides a negative pulse of about 4 kV amplitude and

Journal ArticleDOI
TL;DR: This work surveys some of the existing approaches to optimal design of multivariate sensors, according to the different types of systems they are applied to and discusses two examples of optimal sensor design.
Abstract: The design of sensing systems for the measurement of multiple physical quantities related to a dynamical system is considered. A multivariate sensor comprises several simple transducers, each measuring a scalar quantity that comes from the combination of the components of the quantity to be measured. From the collection of measurements of single transducers at different times, the desired information is extracted by analogue or digital processing. Besides the choice of technological characteristics of the transducers to be employed, the designer of multivariate sensors is usually allowed some freedom in choosing the number of transducers, their arrangement in the system, and the time scheduling of their measurements. These choices are the subject of optimal policies in the design phase, whose goal is to maximize some performance (or minimize some cost) criterion. We survey some of the existing approaches to optimal design of multivariate sensors, according to the different types of systems they are applied to. Two examples of optimal sensor design are discussed as an illustration of the methods.

Journal ArticleDOI
TL;DR: In this article, a mathematical and physical description of a confocal Fabry-Perot interferometer used for the measurement of ultrasound is presented, where the frequency response is derived from a combination of ray types.
Abstract: A mathematical and physical description of a confocal Fabry-Perot interferometer used for the measurement of ultrasound is presented. It analyses the interferometer performance in terms of ultrasonic transfer functions derived for rays of types 1-4. Instrument performance is modelled for two different schemes of operation, namely transmission and reflection. The frequency response is derived from a combination of ray types. In the case of the reflection scheme, a new beam separation method is suggested, which makes full use of the instrument etendue. Additionally, this latter scheme offers a significant increase in sensitivity over a wide frequency range extending towards the free spectral range of the interferometer, typically exceeding 100 MHz.

Journal ArticleDOI
TL;DR: In this paper, the choice of the materials to minimize the deformation of mechanical components caused by extraneous thermal and vibrational inputs is discussed. And a technique for reconciling the conflicting design goals of vibration and thermal distortion is considered.
Abstract: This paper is concerned with the choice of the materials to minimize the deformation of mechanical components caused by extraneous thermal and vibrational inputs. First, material 'performance indices' (combinations of material properties) are derived for systems subjected to low frequency sinusoidal vibration inputs and for systems subjected to broad-band excitation. A methodology is developed for optimizing the choice of material to minimize deformation due to vibration in such systems. Second, materials selection to minimize distortion caused by spurious thermal fluxes is discussed and a performance index which captures the relevant material property combinations is derived. Finally, a technique for reconciling the conflicting design goals of vibration and thermal distortion is considered. The material selection procedure makes use of materials selection charts-a new way of displaying material property data. When combined with the performance indices these allow a number of novel optimization procedures. Section shape can be included, allowing the optimum selection of both material and shape. The method is illustrated through a case study involving selection of a material for the frame of an atomic force microscope with subnanometre resolution.

Journal ArticleDOI
TL;DR: In this paper, a general scheme for an on-line, non-contact, optically based inspection machine has been developed, which has the important attributes of fast measurement, simplicity and flexibility.
Abstract: Examination of various research efforts has revealed that optical techniques best satisfy the requirements of on-line, non-contact inspection; other methods are usually deficient with regard to speed, flexibility and ability to perform non-contact measurement. Of the optical methods considered, techniques based on statistical analysis of scattered light from the sample are best suited for the purpose of surface inspection. A general scheme for an on-line, non-contact, optically based inspection machine has been developed. The system has the important attributes of fast measurement, simplicity and flexibility. The system's roughness measurement capability was successfully tested on ceramic components of varying surface finish.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a total electron yield (TEY) detector which can operate close to liquid nitrogen temperature, which is a data acquisition technique particularly well suited for X-ray spectroscopy measurements performed on coatings.
Abstract: Total electron yield (TEY) in He gas at atmospheric pressure is a data acquisition technique particularly well suited for X-ray spectroscopy measurements performed on coatings. We have developed a TEY detector which can operate close to liquid nitrogen temperature. The novelty of the design consists of a dissociation between the cooling body and the electronic measurement system: the electrically biased collector and the grounded sample are both mounted on a sample holder which is introduced under a permanent He gas flow in the cryostat. Measurements performed on standard pure materials allow investigation of the EXAFs amplitude improvements corresponding to the lowering of the temperature. We also report signal variations observed on thin nanocrystalline films and amorphous alloys.

Journal ArticleDOI
TL;DR: In this article, the design and operating characteristics of a hyperthermal oxygen atom generator are presented and described using a circular filament/reflector assembly to generate the primary electrons responsible for electron stimulated desorption (ESD).
Abstract: The design and operating characteristics of a hyperthermal oxygen atom generator are presented and described. In this source oxygen atoms permeate through a Ag/0.5% Zr membrane at 550 degrees C from a high-pressure region (200 Torr) to the vacuum side of the membrane. There they are emitted toward the target by electron stimulated desorption (ESD). The average O neutral kinetic energy is about 5 eV, and a flux of 4.5*1012 neutrals cm-2 s-1 has been attained using a circular filament/reflector assembly to generate the primary electrons responsible for ESD. The primary electron current required to generate this O neutral flux is 3 mA. The flux produced is very high purity but does contain a relatively small number of O+ and possibly H2O+ or F+. A computer simulation of the charged particle trajectories was used to design the filament/reflector assembly. The simulation studies indicate that a uniform primary electron flux is attained across the membrane, that the secondary electrons are trapped by the source, and that positive ions can be removed from the neutral flux by placing a negative potential on the membrane. Over the range examined, the O neutral flux increases linearly with primary electron current indicating that the overall process is ESD limited rather than limited by the O permeation rate.

Journal ArticleDOI
TL;DR: In this article, the results of outdoor experiments over a period of more than one year are summarized for most of the commercially available types of capacitive air humidity sensors, and it is estimated that 70-75% employ a capacitive type of sensor.
Abstract: Capacitive air humidity sensors have emerged in increasing numbers, makes and qualities. Of all hygrometers available at present, it is estimated that 70-75% employ a capacitive type of sensor. In this paper the results of outdoor experiments over a period of more than one year are summarized for most of the commercially available types.

Journal ArticleDOI
TL;DR: In this paper, a novel form of imaging steel reinforcing components in concrete is described which employs a scanning inductive sensor and a host computer, linked to the scanning and data acquisition system, generates grey-scale images whose intensities are proportional to the signal strengths produced by the sensor.
Abstract: A novel form of imaging steel reinforcing components in concrete is described which employs a scanning inductive sensor. A host computer, linked to the scanning and data acquisition system, generates grey-scale images whose intensities are proportional to the signal strengths produced by the sensor. Simple signal subtraction algorithms have been employed to achieve considerable improvements in image contrast, spatial resolution and the extraction of dimensional information. Models of the sensor response suggest that with further signal manipulation, detailed quantitative measurements on image features will also be possible.

Journal ArticleDOI
TL;DR: In this article, the design and construction of an X-Y position-sensitive detector based on a delay-line anode assembly mounted behind a multichannel plate electron multiplier are described.
Abstract: The design and construction of an X-Y position-sensitive detector based on a delay-line anode assembly mounted behind a multichannel plate electron multiplier are described. The dead-time is less than 60 ns for all particle pairs, and can easily be reduced further.

Journal ArticleDOI
TL;DR: In this article, various techniques for measurement of oxygen concentration/partial pressure using sensors employing zirconia electrolytes are reviewed, including the use of a solid electrolyte cell incorporating two electrodes on each opposing side.
Abstract: The various techniques for measurement of oxygen concentration/partial pressure using sensors employing zirconia electrolytes are reviewed. Zirconia-based air-to-fuel ratio sensors used in combustion applications are also discussed. A solid electrolyte cell incorporating two electrodes on each opposing side may be used as a potentiometric oxygen sensor; this requires a reference gas and provides a logarithmic output. An oxygen pump-gauge device normally consists of two solid electrolyte cells assembled to enclose an internal volume. Pump-gauge devices can be operated in various modes requiring simple electronic circuitry. Devices operating in steady state modes incorporate a diffusion path between the internal volume and the sample gas and provide an output proportional to the oxygen concentration in the sample gas. Pump-gauges operating in oscillatory modes may be fully sealed or may incorporate a diffusion path; they enable both oxygen concentration and partial pressure to be determined.

Journal ArticleDOI
Koji Asami1
TL;DR: In this paper, the capacitance and conductance of colloidal particles and membranes in an aqueous environment are measured by the three-terminal (guarded electrode) method with a coaxial probe electrode, which is laterally scanned over samples on a plate electrode.
Abstract: This article describes a new instrument to image the local capacitance (or permittivity) and conductance (or conductivity) of colloidal particles and membranes in an aqueous environment. Capacitance and conductance are measured by the three-terminal (guarded electrode) method with a coaxial probe electrode, which is laterally scanned over samples on a plate electrode. The images of capacitance and conductance are obtained at frequencies between 1 kHz and 10 MHz, which enables the study of dielectric relaxation of individual particles and local areas of membranes.