Showing papers in "Measurement Science and Technology in 1998"
TL;DR: The first edition of this book as mentioned in this paper was published in 1992 and was used for the first year of a physics course at the University of Sheffield. But it was not intended to be a statistics text, nor was it intended to serve as a statistic text, but an introdution to the mathematics required for the analysis of measurements at the level of a first year laboratory course.
Abstract: Students in a science or engineering curriculum ought to be introduced early to the requirement that a meaningful measurement result should always be accompanied by a statement of its uncertainty. This book has been written specifically with this objective in mind. That the first edition has been successful in doing this is attested to by its popularity with both faculty and students, and its translation into six languages. This book is not a statistics text - nor was it intended to be - but an introdution to the mathematics required for the analysis of measurements at the level of a first-year laboratory course. Part 1 begins with uncertainty as a qualitative concept and builds slowly, using many numerical examples and exercises for the student, to develop methods for quantifying uncertainty, and ultimately relating it to the standard deviation of a statistical distribution. Along the way, Taylor develops the rules for expressing and combining (`propagating') uncertainties, and introduces the student to the gaussian (normal) distribution and some of its properties. Part 2 covers, with somewhat more mathematical rigor, specific topics such as data rejection criteria, the binomial and Poisson distributions, covariance and correlation, least-squares fitting, and the chi-squared test. I was not familiar with the first edition, and from a quick scan of the Preface I looked forward to reading this book and learning something about the state of statistical analysis in first-year university texts today. I was disappointed (in part with what the level of the book implies about the sad state of preparation of today's students). Although there are now two ISO publications ( International Vocabulary of Basic and General Terms in Metrology (VIM) and Guide to the Expression of Uncertainty in Measurement (GUM), Geneva, 1993), Taylor makes no mention of either, and never gives a formal definition of `uncertainty' (although he ultimately associates `random uncertainty' with the standard deviation of a gaussian distribution). The book also does not clearly define `error', or the distinction between error and uncertainty. The important point, that the `propagation of uncertainty' is additive in terms of variances is valid for any distributions with finite variance, is not emphasized; instead Taylor restricts the discussion solely to the normal distribution and or those that can be approximated by it. I also find it unfortunate that the book does not clearly distinguish between the variance of a sample , the variance of a distribution , and the sample estimate of the variance of the distribution ( or ). Instead, he accepts the fact that formulas for the variance with either N or N - 1 dividing the sum of the squares of the deviations from the mean exist in the literature and concludes simply: `Nevertheless, you need to be aware of both definitions. In the physics laboratory, using the more conservative... def- inition... is almost always best.' In spite of these shortcomings, the book is a significant contribution to a student laboratory reading list, and it is written at a level that facilitates a self-study program. It has an important message to deliver and it appears to be delivering it well.
2,637 citations
TL;DR: Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy, suggesting likely directions for future research and development.
Abstract: Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room-temperature mid-IR materials and broadly tunable multisection devices is reviewed to suggest new sensor possibilities.
560 citations
TL;DR: In this paper, the Rayleigh-Ritz technique was employed to find a rigorous relationship between permittivity, resonant frequency, and the dimensions of the resonant structure, with relative computational accuracy of less than.
Abstract: An application of a mode dielectric resonator is described for precise measurements of complex permittivity and the thermal effects on permittivity for isotropic dielectric materials. The Rayleigh-Ritz technique was employed to find a rigorous relationship between permittivity, resonant frequency, and the dimensions of the resonant structure, with relative computational accuracy of less than . The influence of conductor loss and its temperature dependence was taken into account in the dielectric loss tangent evaluation. Complex permittivities of several materials, including cross-linked polystyrene, polytetrafluoroethylene, and alumina, were measured in the temperature range of 300-400 K. Absolute uncertainties of relative permittivity measurements were estimated to be smaller than 0.2%, limited mainly by uncertainty in the sample dimensions. For properly chosen sample dimensions, materials with dielectric loss tangents in the range of to can be measured using the mode dielectric resonator.
391 citations
TL;DR: In this paper, an advanced displacement measuring interferometer system was developed to satisfy the needs of semiconductor manufacturing and lithography, which provides position resolution of 0.31 nm at velocities up to 2.1 m when the system is used with a double-pass inter-ferometer.
Abstract: An advanced displacement measuring interferometer system has been developed to satisfy the needs of semiconductor manufacturing and lithography. The system electronics provides a position resolution of 0.31 nm at velocities up to 2.1 m when the system is used with a double-pass interferometer. Output data rates up to samples per second are available. The data age, which is the delay from the interferometer optics to the measurement sample, can be adjusted to equalize differences between axes to within 1 ns. This low data age uncertainty is necessary for high-resolution, high-speed, multiple-axis measurements.
185 citations
TL;DR: In this paper, the authors used an electronic nose to predict the class and growth phase of two potentially pathogenic micro-organisms, E. coli and Staphylococcus aureus.
Abstract: An investigation into the use of an electronic nose to predict the class and growth phase of two potentially pathogenic micro-organisms, Eschericha coli ( E. coli) and Staphylococcus aureus ( S. aureus), has been performed. In order to do this we have developed an automated system to sample, with a high degree of reproducibility, the head space of bacterial cultures grown in a standard nutrient medium. Head spaces have been examined by using an array of six different metal oxide semiconducting gas sensors and classified by a multi-layer perceptron (MLP) with a back-propagation (BP) learning algorithm. The performance of 36 different pre-processing algorithms has been studied on the basis of nine different sensor parameters and four different normalization techniques. The best MLP was found to classify successfully 100% of the unknown S. aureus samples and 92% of the unknown E. coli samples, on the basis of a set of 360 training vectors and 360 test vectors taken from the lag, log and stationary growth phases. The real growth phase of the bacteria was determined from optical cell counts and was predicted from the head space samples with an accuracy of 81%. We conclude that these results show considerable promise in that the correct prediction of the type and growth phase of pathogenic bacteria may help both in the more rapid treatment of bacterial infections and in the more efficient testing of new anti-biotic drugs.
184 citations
TL;DR: In this paper, a number of methods by which the parameters of the mathematical model of the system are estimated and the application of the Fisher information matrix is described, including the use of Fisher information matrices for thermal property estimation.
Abstract: Optimal experiment design is the definition of the conditions under which an experiment is to be conducted in order to maximize the accuracy with which the results are obtained. This paper summarizes a number of methods by which the parameters of the mathematical model of the system are estimated and describes the application of the Fisher information matrix. Examples are given for thermal property estimation in which the estimation is affected both by measurement noise, which is present during any experiment, but also by uncertainties in the parameters of the model used to describe the system.
176 citations
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TL;DR: A multichannel taste sensor, namely an electronic tongue, with global selectivity is composed of several kinds of lipid/polymer membranes for transforming information about substances producing taste into electrical signals, which are input to a computer.
Abstract: A multichannel taste sensor, namely an electronic tongue, with global selectivity is composed of several kinds of lipid/polymer membranes for transforming information about substances producing taste into electrical signals, which are input to a computer. The sensor output exhibits different patterns for chemical substances which have different taste qualities such as saltiness, sourness and bitterness, whereas it exhibits similar patterns for chemical substances with similar tastes. The sensor responds to the taste itself, as can be understood from the fact that taste interactions such as the suppression effect, which appears for mixtures of sweet and bitter substances, can be reproduced well. The suppression of the bitterness of quinine and a drug substance by sucrose can be quantified. Amino acids can be classified into several groups according to their own tastes on the basis of sensor outputs. The tastes of foodstuffs such as beer, coffee, mineral water, milk, sake, rice, soybean paste and vegetables can be discussed quantitatively using the taste sensor, which provides the objective scale for the human sensory expression. The flavour of a wine is also discriminated using the taste-odour sensory fusion conducted by combining the taste sensor and an odour-sensor array using conducting polymer elements. The taste sensor can also be applied to measurements of water pollution. Miniaturization of the taste sensor using FET produces the same characteristics as those of the above taste sensor by measuring the gate-source voltage. Use of the taste sensor will lead to a new era of food and environmental sciences.
153 citations
TL;DR: In this article, a long-range atomic force microscope (AFM) profiler system was built based on a commercial metrology AFM and a home-made linear sample displacement stage, consisting of monolithic flexures forming a double parallelogram.
Abstract: A long-range atomic force microscope (AFM) profiler system was built based on a commercial metrology AFM and a home-made linear sample displacement stage. The AFM head includes a parallelogram-type scanner with capacitive position sensors for all three axes. A reference cube located close to the tip acts as the counter electrode for the capacitive sensors. Below this metrology AFM head we placed a linear sample displacement stage, consisting of monolithic flexures forming a double parallelogram. This piezo actuated stage provides a highly linear motion over m. Its displacement is simultaneously measured by a capacitive position sensor and a differential double-pass plane mirror interferometer; both measuring systems have subnanometre resolution capability. For the measurement of periodical structures two operating modes are possible: a direct scanning mode, in which the position of the displacement stage is increased point by point while the AFM head measures the height, and a combined scanning mode where the displacement stage produces offsets which are multiples of the pitch to be measured while the AFM head is simultaneously scanning to locate an edge or a line centre position. Construction details, system characteristics and results from first pitch measurements are presented. The estimated relative combined uncertainties for pitch values on different standards are in the range to . Laser diffraction measurements of comparable uncertainty were performed on the same standards and show a very good agreement.
145 citations
TL;DR: In this article, an electronic tongue consisting of a reference electrode, an auxiliary electrode and five wires of different metals (gold, iridium, palladium, platinum and rhodium) as working electrodes was used to follow the deterioration of the quality of milk due to microbial growth when milk is stored at room temperature.
Abstract: We describe an electronic tongue which consists of a reference electrode, an auxiliary electrode and five wires of different metals (gold, iridium, palladium, platinum and rhodium) as working electrodes. The measurement principle is based on pulsed voltammetry, in which successive voltage pulses of gradually changing amplitudes are applied to the working electrodes connected in a standard three-electrode configuration. The five working electrodes were successively connected and corresponding current-response transients are recorded. The electronic tongue was used to follow the deterioration of the quality of milk due to microbial growth when milk is stored at room temperature. The data obtained were treated with principal component analysis and the deterioration process could clearly be followed in the diagrams. To make models for predictions, projections to latent structure and artificial neural networks were used. When they had been trained, both models could satisfactorily predict the course of bacterial growth in the milk samples.
140 citations
TL;DR: In this paper, two optical methods of confocal microscopy for highly accurate characterization of surfaces are presented, and the first method works on measurement fields of less than 1 and is in practice equivalent to the mechanical stylus instrument, even on rough surfaces.
Abstract: Optical non-contact techniques are very interesting for 3D characterization of sensitive and complex engineering surfaces. Unfortunately, the application of optical techniques was for many years restricted to selected types of surfaces which have only moderate variations of height and surface slope relative to their lateral resolution and measurement field. Owing to the fact that artefacts and form deviations occur with high spatial frequencies in optically measured topographs, there were some difficulties in interpreting the results and comparing them with the tactile standard techniques for surface characterization. Furthermore, artefacts in optically measured profiles have often been misinterpreted in terms of the resolution of optical techniques being higher than that of the tactile techniques. This paper presents two optical methods of confocal microscopy for highly accurate characterization of surfaces. The first method works on measurement fields of less than 1 and is in practice absolutely comparable to the mechanical stylus instrument, even on rough surfaces. For this method results compare very well not only in surface statistics but also in topographic raw data, as will be demonstrated for the PTB roughness standards. The second method works on measurement fields up to square centimetres.
139 citations
TL;DR: Inverse techniques as mentioned in this paper are an emerging suite of methods which, when fully embraced, promise to provide better experiments and improved understanding of physical processes, and they can provide better understanding of the physical processes.
Abstract: The main purpose of this paper is to introduce the five following papers on inverse problems, and to relate the field of inverse problems to measurements. Inverse techniques are an emerging suite of methods which, when fully embraced, promise to provide better experiments and improved understanding of physical processes. This paper provides an overview of the general procedure and concepts related to identification of parameters or functions by inverse techniques. A discussion of errors and their implication for an appropriate function for minimization in inverse procedures is presented, and two methods for achieving this minimization are discussed. Some sequential concepts for parameter estimation are presented, along with a discussion of residuals and confidence intervals. Experiment design and optimization are reviewed, and a discussion of residuals and their relation to model building is presented.
TL;DR: In this article, the authors present a very concise compilation of physical parameters of many ''classical'' and ''novel'' optical materials, laser-active ones included, and compare and carefully evaluate the data when several sources are available.
Abstract: This book presents a very concise compilation of physical parameters of many `classical' and `novel' optical materials, laser-active ones included. Until now, there has been no comparable data source on the market. Optical technologies have grown extremely fast since the advent of lasers and nonlinear optics. In the last decade, optics has become a leading technology in communication, information storage, material processing and measuring procedures. On one hand, fundamental discoveries and inventions in the fields of lasers and nonlinear optics provided important preconditions for this development. On the other hand, however, only great progress in material sciences and technologies have made possible the rapid transfer of new light sources and optical devices from R&D laboratories to real-world application. High homogeneity and cleaness of materials and the precise knowledge of their decisive optical, mechanical, thermal, electronic and magnetic parameters have become important, and critical in gaining technological success. Overall performance, and particularly and reliability of devices and systems depend critically on the right use of the right material. For instance, successes in today's ultralong-distance optical-fibre communication systems originate first of all from progress in producing low-loss optical glass fibers and reliable semiconductor lasers. Thus not only physicists, but also engineers urgently need reliable source of such parameters when desiging, developing and constructing devices and systems containg lasers, optical, electo-optical and opto-electronic components. `Properties of optical and laser-related materials' comprises optical and other material parameters with relevance to the performance of lasers and devices in well-ordered tables. The ordering of material properties as well as units and conversion factors are briefly explained in an introductory chapter. A short compilation of important equations in which the respective parameters appear would have been of value to the user, compare for example, the handbooks cited in the introduction and Landoldt Bornstein. The author refers to more than 1000 original papers where he compares and carefully evaluates the data when several sources are available. Here I would like to mention that the author himself if a very successful scientist with experience in laser physics, nonlinear optics and laser spectroscopy. He and his colleagues contributed much to the results contained in this volume, for instance, very useful data on laser damage thresholds and optical nonlinearities. Among the materials to which the data refer are lasing dielectric crystals and semiconductors, high-transparency optical crystals, glasses and polymers, efficient second-order nonlinear optical crystals as well as specifically selected liquids and gases. Author and publisher are kindly asked to publish future editions also on compact disk which would allow easy processing of data by the user as well as frequent up dating of the whole content by the editor. In summary, I recommend this book to all physicists and engineers who design or use linear and nonlinear optical devices and components.
TL;DR: In this article, the authors proposed a method to measure any length absolutely and accurately, by combining a high-resolution phase measurement technique with a frequency scanning technique, which achieved high resolution, higher than quarter wavelength, using the wide-range frequency scanning method.
Abstract: It is easy to measure length accurately by means of optical interferometry. However, the measurement range of a single-frequency interferometer is limited to less than half the wavelength without a moving carriage to count interference fringes. To resolve this problem, a frequency scanning method had been developed. However, its phase resolution is not so high that the integer part of the order of the interference fringe can be accurately determined. We proposed a method to measure any length absolutely and accurately, by combining a high-resolution phase measurement technique with a frequency scanning technique. In this paper, this method was investigated by using a frequency scanning heterodyne interferometer. With heterodyne phase measurement, we achieved high resolution, higher than quarter wavelength, using the wide-range frequency scanning method. This means that we can measure the absolute length with nanometre accuracy, since the integer part of the order of the interference fringe for a wavelength is determined with the frequency scanning. We measured distances up to about 4 mm with an accuracy of about 3 nm.
TL;DR: In this paper, a new highly precise angle measuring table has been developed for the Physikalisch-Technische Bundesanstalt, which is to be used as a comparator to calibrate angle standards.
Abstract: A new highly precise angle measuring table has been developed for the Physikalisch-Technische Bundesanstalt, which is to be used as a comparator to calibrate angle standards. First results of the determination of the comparator's errors of measurement obtained by two calibration methods are reported. Considering the results obtained, it is to be expected that the desired uncertainty of measurement of can be achieved.
TL;DR: In this paper, a pulsed electro-acoustic system is described which enables electric fields up to to be generated in thin (100-) insulating plaque samples with measurement of the dynamic net space charge density, as a function of temperature and of distance through the thickness of the sample, and the external circuit charging current.
Abstract: A pulsed electro-acoustic system is described which enables electric fields up to to be generated in thin (100-) insulating plaque samples with measurement of the dynamic net space charge density, as a function of temperature and of distance through the thickness of the sample, and the external circuit charging current. From these measurements, the dynamic electric field, potential and conduction current density distributions within low-density polyethene samples have been obtained and are reported.
TL;DR: In this article, a diode-laser sensor system was developed to measure the concentrations of NO, O, CO, and in combustion gases using absorption spectroscopy and fast extraction sampling techniques.
Abstract: A diode-laser sensor system has been developed to measure the concentrations of NO, O, CO, and in combustion gases using absorption spectroscopy and fast-extraction sampling techniques. Measured survey spectra of the NO 3 band (the R branch) and O lines from the band in the spectral region from 5556 to 5572 were recorded and compared with calculated spectra to select optimum transitions for detection of NO. Similarly, measured survey spectra of the O 3 band from 6535 to 6600 were used to identify optimum transitions for detection of O. High-resolution NO absorption measurements ((7.5) and (7.5) lines) were recorded in a fast-flow multipass cell containing probe-sampled combustion gases to determine NO concentrations in a laminar, premixed -air flame, seeded with . For fuel-lean conditions, the measured NO mole fractions corresponded to 68% of the injected . For fuel-rich conditions, the fraction of converted to NO decreased with increasing equivalence ratio. In additional experiments, CO, and absorption measurements (the R(13) line of the 3 band, the R(16) line of the band and the RQ(7, 8) line of the b band, respectively) were used to determine species concentrations above a laminar, premixed -air flame. Good agreement was found between measured CO, and concentrations and calculated chemical equilibrium values.
TL;DR: In this article, a simple, low-cost all-fibre grating strain sensing interrogation technique is proposed, which offers high static-strain resolution and large dynamic range.
Abstract: We report here a simple, low-cost all-fibre grating strain sensing interrogation technique offering high static-strain resolution and large dynamic range . A key interrogating component of this technique is a long-period grating which acts as an edge filter converting strain-induced wavelength variation into optical power measurement. The transmission profile of the long-period grating is shown to be nearly linear over a sufficiently wide range, yielding a linear relationship between the resultant intensity and applied strain, and a high resolution achieved by standard lock-in techniques.
TL;DR: In this paper, a high-resolution distance meter was fabricated using optical waveguide modulators and an optical intensity modulation frequency of 28 GHz was utilized for the displacement measurement when the driving frequencies to the optical modulators were around 14 GHz.
Abstract: A high-resolution distance meter was fabricated using optical waveguide modulators. An optical intensity modulation frequency of 28 GHz was utilized for the displacement measurement when the driving frequencies to the optical modulators were around 14 GHz. The distance meter was evaluated in the National Research Laboratory of Metrology (NRLM) tunnel, which is a semi-underground tunnel. The measurement resolution is 1 and for a distance of 5 and 100 m, respectively, in one standard deviation after correction of the cyclic error. Furthermore, cyclic errors are examined for 28 GHz optical intensity modulation.
TL;DR: In this paper, a method based on nondestructive microwave characterization is used for simultaneous determination of the bulk density and moisture content of shelled corn, regardless of the measurement technique and thus considerably simplifies the calibration procedure.
Abstract: A method based on nondestructive microwave characterization is used for simultaneous determination of the bulk density and moisture content of shelled corn. This method can be applied regardless of the measurement technique and thus considerably simplifies the calibration procedure. Calibration equations, both for the bulk density and for the moisture content, are given, together with the standard error of performance (SEP) at several frequencies in the range 11-18 GHz and three temperatures, 14, 24 and C. The bulk density, ranging from 695 to , can be determined with SEP in the range 11-. Neither the sample moisture content nor its temperature are required in order to determine the bulk density. The moisture content ranging from 9% to 19% on a wet basis, can be determined at each temperature without knowledge of the bulk density with SEP of less than 0.5% moisture content. Results of an error analysis of the measurements show that about half of the total uncertainties in bulk density and moisture content can be considered systematic errors and thus they are correctable.
TL;DR: In this article, the authors reviewed the development of spatial light scattering analysis as an analytical and monitoring tool now finding application in areas as diverse as environmental monitoring, aerosol and hydrosol research, microbiology and fine-powder characterization.
Abstract: The manner in which a particle scatters incident light is a function of the particle's shape, its size, its structure and its orientation with respect to the illumination direction, as well as to the wavelength and polarization state of the light. The spatial intensity distribution of scattered light thus contains information by which the particle may often be classified or even identified. This paper briefly reviews the development of spatial light scattering analysis as an analytical and monitoring tool now finding application in areas as diverse as environmental monitoring, aerosol and hydrosol research, microbiology and fine-powder characterization. The paper concludes with a practical example of the use of spatial scattering analysis to achieve real-time discrimination of a specific particle type, namely airborne asbestos fibres.
TL;DR: In this article, a three-dimensional coordinate of a target position was measured using a laser tracking interferometer system based on laser trilateration, which is mounted on two-directional rotating stages, track the motion of the target retroreflector.
Abstract: A three-dimensional coordinate of a target position was measured using a laser tracking interferometer system based on laser trilateration. Laser interferometers, which are mounted on two-directional rotating stages, track the motion of the target retroreflector. By applying the principle of trilateration, the position of the retroreflector is estimated using the optical path difference caused by the motion of the target. Four laser interferometers were used, which produced redundancy in the measurement. By taking advantage of the redundancy, the position of the interferometers and the initial position of the target is self-calibrated and consequently the target position was calculated. The measurement error of a preliminary experiment was about m for a 1 m measurement.
TL;DR: In this paper, the PTB has developed a new pattern placement metrology instrument using a high-resolution electron beam probe, which consists of a lowvoltage scanning electron microscope with a large vacuum chamber and a 300 mm x-ypositioning stage, controlled by vacuum laser interferometry.
Abstract: The demands on the uncertainties of pattern placement and overlay measurements in lithography are constantly growing due to the continuing reduction of feature size which allows higher density integration. Although nowadays optical projection lithography plays the dominant role in lithography and will continue to do so in the near future other technologies will be developed further in order to replace optical lithography soon after the beginning of the next century. A pattern placement metrology instrument should be able to perform measurements on the masks used today as well as on future types of lithography masks. The PTB has developed a new pattern placement metrology instrument using a high-resolution electron beam probe. The electron optical metrology system consists of a low-voltage scanning electron microscope with a large vacuum chamber and a 300 mm x-y-positioning stage, controlled by vacuum laser interferometry. The design principles of the instrument will be described and a comparison of measurements with those of an optical mask measuring system will be presented.
TL;DR: In this article, an improved technique for measuring gear transmission error (GTE) at high speed, by using low pulse per revolution optical encoders, was presented. But, the accuracy of the measurement was limited to only 0.03 second of arc for each frequency of the power spectral density, and the correlation between the two measurements is less than 3% of the magnitude of the relative eccentricity.
Abstract: We evaluated in this paper an improved technique for measuring gear transmission error (GTE) at high speed, by using low pulse per revolution optical encoders. The originality of this technique lies in the fact that highly precise, completely digital measurements of torsional vibration or transmission error (TE) at high speed are achievable by the use of low-price, basic optical components. The lengths of encoder pulses are estimated with a high-frequency timer (100 MHz): thus, it appears that the theoretical precision of this device depends only on the angular speed of shafts, not on the number of pulses per revolution of the encoder. In practice, the intrinsic encoder accuracy (namely the grating or electronic signal processing precision) directly affects precision measurements. Alternatively, the number of pulses per revolution of the encoder specifies the resolution. We examined the possibility of calibrating encoders through using a specific test rig. The determination of corrective data assigned to each grating leads to an insignificant improvement of the precision measurement. The coherence from one revolution to another does not present any significant deterministic component. The overall precision achieved is less than 0.03 second of arc for each frequency of the power spectral density. This calibration device only gives a good assessment of eccentricity induced by mechanical mounting of optical discs on a shaft, compared with the direct measurement on grating discs. The correlation between the two measurements is less than 3% of the magnitude of the relative eccentricity. Thus, the encoder technique seems to be a cheap and easy way to implement transmission error measurement on real mechanical systems with high precision and sufficient reliability.
TL;DR: In this article, density-independent calibration functions are proposed for problems involving variation of bulk density in on-line determination of the moisture content in particulate materials by microwave techniques and their effectivenesses for prediction of moisture content are compared and optimum conditions for a cost-effective moisture meter are discussed.
Abstract: Density-independent calibration functions are a suitable solution for problems involving variation of bulk density in on-line determination of the moisture content in particulate materials by microwave techniques. Foundations of three of these functions are briefly reviewed and their frequency and temperature dependences are shown for wheat. Their effectivenesses for prediction of the moisture content are compared and optimum conditions for a cost-effective moisture meter are discussed.
TL;DR: In this paper, the fabrication of prototype thick film silver-silver chloride electrochemical reference electrodes is described, where combinations of commercially available and proprietary thick film pastes have been used in their construction in a multi-layer planar configuration modelled upon the structure of the classic single junction silver- silver chloride reference electrode cell.
Abstract: The fabrication of prototype thick film silver-silver chloride electrochemical reference electrodes is described. Combinations of commercially available and proprietary thick film pastes have been used in their construction in a multi-layer planar configuration modelled upon the structure of the classic single junction silver-silver chloride reference electrode cell. Several variations in the basic electrode design were fabricated, involving combinations of one of three different paste formulations for the silver-silver chloride layer coupled with one of two combinations of paste formulation for the salt containment matrix. The relative performances of these different versions of reference electrode were evaluated in terms of their chloride ion sensitivity, hydration times required to achieve a stable potential and usable lifetime. It is shown that, depending on the processing methodology employed at certain stages in the fabrication of these devices, a large degree of variation in characteristics can be achieved and therefore exploited in the design of reference electrodes suitable for a range of specific applications.
TL;DR: In this paper, an ultrasonic constant-beamwidth transducer system which is capable of generating an extended focal zone by electronically focusing the beam over the desired water-depth range is described.
Abstract: An ultrasonic constant-beam-width transducer system which is capable of generating an extended focal zone by electronically focusing the beam over the desired water-depth range is described Beam directivity measurements show that the higher beam directivity and the reduction in side-lobe level lead to an increase of the signal-to-noise ratio by up to 15 dB compared with that of a plane disc transducer It also allows one to attain a significant reduction of undesirable spectral broadening effects which in the case of plane disc transducers lower the final resolution and interfere with the correct interpretation of data Using the focalized transducer, simultaneous 3D velocity component profile measurements over the whole water depth are carried out in uniform, open-channel flow and reveal the presence of coherent structures In the transversal direction, a stationary secondary current composed of two stationary vortices is observed Compared with a plane disc transducer system, the focalized system increases the resolution by up to 50%
TL;DR: In this paper, a real-time PC-based machine vision algorithm and hardware implementation is presented that achieves measurements of cell rotational motion and analysis of ROT spectra in less than 5 min, taking four measurement points per frequency decade.
Abstract: Electrorotation (ROT) has been applied widely for determining the dielectric properties of cells (and bio-particles) with single-cell resolution. However a serious limitation of ROT has been the tedious manual measurements required. A new real-time PC-based machine vision algorithm and hardware implementation are presented that achieve measurements of cell rotational motion and analysis of ROT spectra. The system is equipped with a computer-controlled quadrature digital synthesizer and is capable of measuring a ROT spectrum of a single cell with the frequency range 1 kHz-200 MHz in less than 5 min, taking four measurement points per frequency decade. Laser tweezers are used to facilitate cell selection and positioning in order to maximize the flexibility and accuracy of the system. The performance of this system is characterized in terms of robustness, accuracy and linearity with respect to manual measurements of real spinning cells under the influence of a rotating electric field. The system is quite generally applicable to a wide variety of mammalian cell morphologies and optical appearances. Membrane capacitance values derived from automated ROT measurements averaged within 10% of those obtained from manual measurements.
TL;DR: In this article, a method of isolating a fiber Bragg grating from strain was described, which can then be used to compensate for the temperature cross sensitivity of a FBG strain sensor.
Abstract: This paper describes a method of isolating a fibre Bragg grating (FBG) from strain. This strain-isolated fibre Bragg grating (SIFBG) was then used to make strain-independent temperature measurements. The SIFBG can then be used to compensate for the temperature cross sensitivity of a FBG strain sensor. Initial results using this compensation scheme are presented, demonstrating proof of the principle.
TL;DR: In this paper, an ultrasonic technique was used to study the propagation of wide bandwidth compression and shear wave pulses in a curing adhesive, where a temperature controlled water filled test cell with transducers placed at either end is used to couple ultrasound into a thin sample of adhesive.
Abstract: This paper describes an ultrasonic technique to study the propagation of wide bandwidth compression and shear wave pulses in a curing adhesive. A temperature controlled water filled test cell with transducers placed at either end is used to couple ultrasound into a thin sample of adhesive. A novel sample holder is employed to contain the uncured liquid adhesive between thin polymer films to stop water ingress and a high-precision goniometer is used to align the sample with respect to the transducers. Consecutive normal and oblique incidence measurements are made at intervals during the adhesive cure. The oblique angle is selected to enable a shear wave to be excited in the adhesive sample by mode conversion. This occurs as soon as the adhesive is able to support shear displacements and hence the detection of the transition from liquid to solid state is possible. The compression and shear wave pulses are analysed in the frequency domain using Fourier analysis and this facilitates calculation of the frequency-dependent compression and shear wave absorption coefficients and phase velocities. From these measurements it is possible to calculate the complex bulk and shear moduli. Results are presented for a number of commercially available adhesives, and it is shown that ultrasound data signatures can be related to aspects of cure such as its rate and `gel point', as well as providing quantitative measurement of the elastic moduli.
TL;DR: In this paper, speckle interferometry has been applied to the measurement of Young's modulus in thin films, and the results showed that the results were lower than the polycrystalline bulk average value and electrodeposited films.
Abstract: Speckle interferometry has been applied to the measurement of Young's modulus in thin films. The present study has two novel aspects: the specimens used were approximately 1 m thick and less than 1 mm long, so the speckle images were obtained by photomicroscopy; and the digital images were analysed by quantitative treatment at intense speckles, rather than by the more standard techniques. Displacements and strains within the gauge length were obtained with low statistical uncertainties. Young's modulus values for three varieties of copper thin films were obtained. All were lower than the polycrystalline bulk average value and the electrodeposited film's modulus was lower than those of both the vapour-deposited films.