Showing papers in "Measurement Science and Technology in 1997"

Fundamentals of digital particle image velocimetry

Abstract: The measurement principle of digital particle image velocimetry (PIV) is described in terms of linear system theory. The conditions for PIV correlation analysis as a valid interrogation method are determined. Limitations of the method arise as consequences of the implementation. The theory is applied to investigate the statistical properties of the analysis and to optimize and improve the measurement performance. The theoretical results comply with results from Monte Carlo simulations and test measurements described in the literature. Examples of both correct and incorrect implementations are given.

In-fibre Bragg grating sensors

Abstract: In-fibre Bragg grating (FBG) sensors are one of the most exciting developments in the field of optical fibre sensors in recent years. Compared with conventional fibre-optic sensors, FBG sensors have a number of distinguishing advantages. Significant progress has been made in applications to strain and temperature measurements. FBG sensors prove to be one of the most promising candidates for fibre-optic smart structures. This article presents a comprehensive and systematic overview of FBG sensor technology regarding many aspects including sensing principles, properties, fabrication, interrogation and multiplexing of FBG sensors. It is anticipated that FBG sensor systems will be commercialized and widely applied in practice in the near future due to the maturity of economical production of FBGs and the availability of cost effective interrogation and multiplexing techniques.

Tracer particles and seeding for particle image velocimetry

Abstract: The size specifications for suitable tracer particles for particle image velocimetry (PIV), particularly with respect to their flow tracking capability, are discussed and quantified for several examples. A review of a wide variety of tracer materials used in recent PIV experiments in liquids and gases indicates that appropriately sized particles have normally been used. With emphasis on gas flows, methods of generating seeding particles and for introducing the particles into the flow are described and their advantages are discussed.

Solid state gas sensors

Abstract: The detection and monitoring of gases with solid state sensors has become a well established practice. Three major types of solid state gas sensor are already in widespread use and a number of other designs currently in development may have the potential for commercial exploitation in the future. The established sensor types are reviewed here and a brief description is given of some of the emergent technologies.

Distortion compensation for generalized stereoscopic particle image velocimetry

Abstract: Optical distortion due to inaccurate optical alignment, lens nonlinearity, and/or refraction by optical windows, fluid interfaces, and other optical elements of an experiment causes inaccuracy by introducing variable magnification. Since fractional changes in the magnification have a one-to-one effect on the accuracy of measuring the velocity, it is important to compensate for such distortions. A general experimental calibration procedure is described which determines the magnification matrix of a distorted imaging system, and an algorithm is presented to compute accurate velocity field displacements from measurements of distorted PIV images. These procedures form a basis for generalized stereoscopic PIV procedures which permit easy electronic registration of multiple cameras and accurate recombination of stereoscopic displacement fields to obtain the three-dimensional velocity vector field.

Stereoscopic Digital Particle Image Velocimetry for Application in Wind Tunnel Flows

Abstract: A particle image velocimetry system capable of accurately recovering the out-of-plane velocity component has been realized based on a stereoscopic viewing arrangement. To allow a large viewing angle with long focal length objective lenses, the angular displacement or Scheimpflug imaging configuration is employed in which the image, object and lens planes intersect in a common line. The varying magnification factor associated with this imaging configuration is accounted for using an accurate and simple-to-use calibration procedure based on solving the projection equations for each of the two cameras. A pair of high-resolution cameras, both capable of recording image pairs in the microsecond range, are synchronized to a pulsed Nd-YAG laser. By placing the cameras on either side of the light sheet the favourable light scattering characteristics of micron-sized seeding particles in forward scatter provide images at significantly higher illumination than at normal or backscatter viewing angles. Ultimately designed for use in industrial wind tunnels, the camera system is capable of working with non-symmetric arrangements. It has been successfully tested in a laboratory environment by imaging the unsteady flow field of a vortex ring passing through a laser light sheet. Adaptive processing software capable of dynamically adjusting the sample location of the interrogation windows to the local displacement vector significantly improves data yield. The algorithm requires only the selection of the final window/overlap size. The hierarchical interrogation approach permits the processing of images whose displacement dynamic range exceeds the interrogation window size.

On errors of digital particle image velocimetry

Abstract: The goal of the present study is to quantify and reduce, when possible, errors in two-dimensional digital particle image velocimetry (DPIV). Two major errors, namely the mean bias and root-mean-square (RMS) errors, have been studied. One fundamental source of these errors arises from the implementation of cross correlation (CC). Other major sources of these errors arise from the peak-finding scheme, which locates the correlation peak with a sub-pixel accuracy, and noise within the particle images. Two processing techniques are used to extract the particle displacements. First, a CC method utilizing the FFT algorithm for fast processing is implemented. Second, a particle image pattern matching (PIPM) technique, usually requiring a direct computation and therefore more time consuming, is used. Using DPIV on simulated images, both the mean-bias and RMS errors have been found to be of the order of 0.1 pixels for CC. The errors of PIPM are about an order of magnitude less than those of CC. In the present paper the authors introduce a peak-normalization method which reduces the error level of CC to that of PIPM without adding much computational effort. A peak-compensation technique is also introduced to make the mean-bias error negligible in comparison with the RMS error. Noise in an image suppresses the mean-bias error but, on the other hand, significantly amplifies the RMS error. A digital video signal usually has a lower noise level than that of an analogue one and therefore provides a smaller error in DPIV.

Refractive-index measurements in the near-IR using an Abbe refractometer

Abstract: A novel method to measure the refractive index n in the near-infrared by simple extensions to a standard Abbe refractometer is described. A technique is derived to correct for the dispersion of the glass prism and experimental results of refractive-index measurements at are compared with published data. These results prove the suitability of the described method, the accuracy being comparable to that of an Abbe refractometer used in the visible range; that is, the refractive index n can be measured to an accuracy of . Finally, new refractive-index data at 830 nm are given for methanol, water, acetone, ethanol, cyclohexane, glycol, di-2-ethyl hexyl-sabacate (DEHS), carbon tetrachloride, glycerol, toluene, ethyl salicylate, methyl salicylate and cinnamaldehyde at 20 and .

Dynamic ranges of velocity and spatial resolution of particle image velocimetry

Abstract: To observe instantaneous fields of vorticity and rate-of-strain using PIV (particle image velocimetry) measurements of the velocity field, it is necessary to achieve maximum dynamic ranges in space and in velocity while simultaneously making accurate, low-noise measurements for the differentiation process. In this paper the dynamic ranges achievable with PIV are established in the context of the super-resolution algorithm described previously which seeks to extract the maximum possible information from a particle image field. Bounds on the dynamic spatial range and the dynamic velocity range are established in terms of optical parameters, and simple rules are derived for optimum design of PIV optical systems for various types of image recording media.

The simultaneous measurement of elastic, electrostatic and adhesive properties by scanning force microscopy: pulsed-force mode operation

Abstract: We describe the pulsed-force mode, a new measuring mode for the scanning force microscope to image elastic, electrostatic and adhesive properties simultaneously with topography. The pulsed-force mode reduces lateral shear forces between the tip and the sample. Even very delicate samples can be mapped at high lateral resolution with full control over the force applied to the sample. The achieved scanning speed is comparable to that in contact-mode operation. The pulsed-force mode electronics can easily be added to many microscopes without much alteration of the original set-up. No change of the data acquisition software or of the feedback circuit is necessary.

Thick-film sensors : past, present and future

Abstract: A review of thick-film sensors is presented. The evolution of the technology to a successful enabling mechanism for solid-state sensors is described. Many examples of applications in the major signal domains (mechanical, radiant, thermal, magnetic and chemical) are cited. The important characteristics of the technology relating to hybrid circuits, support structures and primary sensing elements are illustrated. The future of thick-film sensors is discussed in the light of the rapid development of new materials for sensors that have emerged over recent years.

Recent developments in three-phase flow measurement

Abstract: The problem of how to meter oil - water - gas mixtures has been a significant one in the oil industry since the early 1980s. Since then, considerable research has been conducted into the development of a three-phase flowmeter suitable for use in an offshore environment. This work discusses why three-phase flow measurement is important, the principal strategies and technologies which may be used to meter three-phase flows, and reviews the status of some currently available solutions.

3D PTV and its application on Lagrangian motion

Abstract: Three-dimensional particle tracking velocimetry (3D PTV) is a flow measurement technique for the determination of velocity vectors and trajectories within a three-dimensional observation volume. This makes this technique suitable not only for Eulerian but also for Lagrangian investigation of flow phenomena, especially in the field of turbulence and turbulent diffusion. The principle and the application on open channel flow of 3D PTV are briefly described in the first part of this paper. By decomposition of the velocity vectors velocity profiles and turbulence intensities are derived and presented in the second part. Turbulent energy dissipation, Kolmogorov length and time scales and Taylor micro scales are computed from the measured data sets. In the Lagrangian analysis pdf's of the Lagrangian acceleration, correlation coefficients and Taylor micro scales are determined. The individual determination of the particle positions and displacements allows finally the application on the one and two particle approaches for turbulent diffusion from Taylor (1921), Richardson (1926) and Batchelor (1949, 1952).

Three-dimensional particle image velocimetry: experimental error analysis of a digital angular stereoscopic system

Abstract: Experimental error analysis of a digital angular stereoscopic PIV system is presented. The paper firstly describes an experimental rig which includes the design of a novel PIV test block for in situ calibration. This allowed the user to set up a static seeded flow volume which was translated in and out of plane to record PIV images using two megapixel CCD cameras positioned for angular stereoscopic viewing. PIV data were collected for a range of camera angles up to and for a range of flow displacements and processed by cross correlation into a set of two-dimensional calibration and flow displacement vectors. These 2D data were then processed into three-dimensional data by the use of geometric and bicubic spline interpolation algorithms and an error analysis performed on the predicted displacements. Results from this analysis have shown optimum system performance will be obtained by using camera angles of between 20 and and f numbers of f16 and higher. The results have also shown a theoretical prediction of system performance derived in previous work, which considers the ratio of out of plane to in plane errors, matches to within 8 and 18% of the experimental system performance.

Shape measurement by temporal phase unwrapping: comparison of unwrapping algorithms

Abstract: Projected fringes can be used to measure surface profiles unambiguously, even in the presence of surface discontinuities, if the fringe pitch is changed over time. We investigate by numerical, analytical and experimental means the reliability of two recently proposed algorithms for unwrapping the resulting phase histories. The first, which unwraps through a sequence of phase maps produced with a linear change in spatial frequency with time, is found to be superior to the second, which uses only the first and last maps in the sequence. A new method is proposed in which the spatial frequency is changed exponentially with time. It is shown to be significantly more robust than either of the other algorithms under most conditions. The computation time required to unwrap through a given phase range is proportional to and therefore also results in a reduction in computational effort by a factor compared with the linear algorithm.

Three-dimensional particle image velocimetry: error analysis of stereoscopic techniques

Abstract: A geometric error model for analysis and design of stereoscopic PIV systems is presented. The model allows displacement errors in either translational or angular systems to be analysed for any given angle or camera separation and for any off-axis position. A parameter for the analysis of the system performance is also introduced based on the ratio of out-of-plane to in-plane errors. This is subsequently used to investigate the relative performance of translational and angular PIV systems for camera angles up to and camera separations of half the object distance. Results from this analysis show similar trends in centreline characteristics for both types of stereo systems but different trends in off-axis error ratios due to imaging geometry. The results have also suggested that a CCD-based angular PIV stereo system offers up to 40% greater out-of-plane accuracy for a given field of view and laser power than previous translational systems.

Data validation, false vectors correction and derived magnitudes calculation on PIV data

Abstract: Due to the particular features that appear in the vector maps delivered by the PIV method, there are postprocessing steps that can substantially enhance its performance. These steps include: detection of false vectors, correction of these vectors and the calculation of derived flow magnitudes. Many derived magnitudes can be of interest but this work focuses on the calculation of the first spatial derivative, component of flow divergence or vorticity, on a two-dimensional flow configuration. New algorithms, developed for each step, are described, with the aim of jointly applying them in a coherent way. Where applicable, an analytical tool for filter analysis and design is explained. Application to synthetic and real PIV data is presented as well as a performance contrast with other conventional algorithms, in terms of accuracy, frequency response and error propagation, among others.

3D scanning PIV applied to an air flow in a motored engine using digital high-speed video

Abstract: 3D scanning particle image velocimetry (SPIV) provides particle images in a large set of parallel light-sheet planes using a rapid scanning light-sheet which samples the flow in depth from which the three-dimensional flow field can be reconstructed in the scanned volume. Together with a digital high-speed video technique and a high-speed rotating drum scanner for 3D beam scanning, first 3D SPIV measurements were carried out in a motored model engine with a transparent cylinder and piston crown. Attention was focused on the generation of small-scale structures during compression strokes. Using a spatial cross-correlation of particle images in the overlapping sheets, the 3D flow field could be recovered from the sheet-wise tomographic recorded flow volume. This demonstrates the potential of 3D SPIV in engine flows since 3D information can be obtained from a single view and therefore the method can be applied in actual research engines already in use without any additional modification. The first results of the feasibility study have shown complex flow at the very end of compression which is characterized here by meandering monopolar and dipolar vortices within the main swirling flow which interact with the centre. It is suggested that the observed vortex splitting and shearing is an important contribution to the creation of turbulence.

A novel micropump design with thick-film piezoelectric actuation

Abstract: A new design for a silicon-based micropump is described. Passive cantilever valves are produced by boron etch stop and fusion bonding. Tests of these valves show good performance, as no flow could be detected in the reverse direction. Initial experiments on a thick-film screen printed piezoelectric membrane actuator were undertaken. A study of suitable inks for electrodes on different insulation layers on silicon yielded silicon dioxide and cermet gold ink as the most satisfactory combination. Deflection measurements of a mm PZT (lead zirconate titanate) - bimorph membrane gave movement at an applied voltage of 100 V. A quasi-static simulation package of the flow through a micropump is also presented. The valve action is simulated using ANSYS coupled with FLOW3D. The piezoelectric membrane deflection is simulated with ANSYS. A differential equation for the combined actuation of membrane and valves is solved numerically with Maple. Pump rates of up to and a maximum backpressure of up to 70 kPa for a driving voltage of 40 V have been modelled using bulk values for PZT-5H. A pump rate of up to and a maximum backpressure of up to 35 kPa at 100 V driving voltage are predicted using thick-film parameters extracted from the measurements.

New results on the absolute ion detection efficiencies of a microchannel plate

Abstract: Absolute single-particle detection efficiencies and pulse height distributions of a cascaded microchannel plate (MCP) detector are reported for the ions , , , and in the impact energy range 0 - 4.75 keV. The detection efficiencies have been obtained using the photoelectron - photoion coincidence (PEPICO) technique which allows the determination of detection efficiencies without knowledge of the absolute ionization rate. The mean gain is found to increase with increasing ion impact energy and decreasing ion mass. Depending on the ion mass, the absolute detection efficiencies saturate above 2.5 keV and reach about 63%.

A novel instrument to measure acoustic resonances of the vocal tract during phonation

Abstract: Acoustic resonances of the vocal tract give rise to formants (broad bands of acoustic power) in the speech signal when the vocal tract is excited by a periodic signal from the vocal folds. This paper reports a novel instrument which uses a real-time, non-invasive technique to measure these resonances accurately during phonation. A broadband acoustic current source is located just outside the mouth of the subject and the resulting acoustic pressure is measured near the lips. The contribution of the speech signal to the pressure spectrum is then digitally suppressed and the resonances are calculated from the input impedance of the vocal tract as a function of the frequency. The external excitation signal has a much smaller harmonic spacing than does the periodic signal from the vocal folds and consequently the resonances are determined much more accurately due to the closer sampling. This is particularly important for higher pitched voices and we demonstrate that this technique can be markedly superior to the curve-fitting technique of linear prediction. The superior frequency resolution of this instrument which results from external vocal tract excitation can provide the precise, stable, effective, articulatory feedback considered essential for some language-learning and speech-therapy applications.

A 4.2 K receiver coil and SQUID amplifier used to improve the SNR of low-field magnetic resonance images of the human arm

Abstract: We describe the design and use of a 48 mm diameter, liquid-helium-cooled MRI receiver coil and DC SQUID pre-amplifier. Comparison of images of a non-conducting room temperature test object collected with the SQUID-based system and those collected with an equivalent-area room-temperature surface coil show that the SQUID system SNR is approximately a factor of four greater, despite a 15 mm vacuum gap between sample and coil in the SQUID case. SQUID images of the lower arm also display improved SNRs over those of the room-temperature coil, this time by a factor of between two and three, and as a result reveal greater anatomical detail. We show that the performance is currently limited by inductively coupled losses from metal components in the imager, but that, by using the same system in a whole-body imager, the SNR of SQUID images of the arm will exceed the room-temperature coil's performance by a factor of between 2.8 and 4.5. We believe that these are the first magnetic resonance images of a living sample to have been produced with a SQUID-based receiver.

Refractive index errors in the critical-angle and the Brewster-angle methods applied to absorbing and heterogeneous materials

Abstract: High-precision critical-angle refractometers, with automatic refractive index computation and readout, are now available from several manufacturers. In such instruments light is incident from within a transparent reference medium, typically an optical prism, onto a sample material in good optical contact with the prism. The critical angle of reflection is measured at the interface between the prism of known refractive index and the sample material of unknown refractive index. Critical-angle refractometers are calibrated for transparent samples but are commonly used for measurements of refractive index in optically absorbing or optically heterogeneous materials. The instrument will then read an apparent refractive index which differs from the true refractive index of the sample. The optics of the critical-angle refractometer are investigated to quantify errors which arise from the neglect of absorption and heterogeneity in the transparent sample interpretation of the critical angle. Refractive index reading errors will be important when they become larger than the refractive index precision of modern instruments, about . In critical-angle refractometry it is shown that this occurs for samples of surprisingly weak absorption. The critical-angle and Brewster-angle methods are compared for optically absorbing and heterogeneous samples. Errors arising from sample absorption in the Brewster-angle method are shown to be much less than in the critical-angle method.

The Quantum Theory of Measurement (2nd edn)

Abstract: The newly revised edition of this well-known book categorizes prevalent views on measurement as described by quantum mechanics, discusses basics agreed to by many who on other issues disagree, and describes some of the problems. Although many paragraphs rest unchanged from the first (1991) edition, results found since 1991 are used to reorganize and sharpen the focus of the book, so that even the old paragraphs are now understood differently and more clearly. One advance in the second edition is a new and more general no-go theorem; another is separation of formal derivations from interpretation. The dozen or so definitions essential to following the book even casually are stated clearly. By this means the authors succeed pretty well in achieving their stated desire to make the book comprehensible to those who do not share their philosophic predispositions. While I differ in philosophy from the authors, attending to their discussion uncovered weaknesses in my own thinking and improved it. The mathematical language of quantum mechanics expresses a system under measurement by states (as rays in a Hilbert space) and a hamiltonian operator, distinct from the apparatus that produces outcomes, which is expressed by a positive operator-valued (POV) measure. In this way quantum language separates state preparation from state measurement. Often the Hilbert space is viewed as a tensor product of subspaces, allowing further conceptual separations. The authors take the stance that quantum mechanics calls for splitting the empirical world into parts, the most essential being (1) objective systems S (to be observed) and (2) apparatus A (preparation and registration devices that produces outcomes (or, as the authors write, definite pointer values) of the observed system). In some interpretations, one or both of an observer and an environment appear as additional parts. What is to be included in the system S versus the apparatus A is not specified by the language, but is open to the theoretician; a probe, for example, can be analysed as either part of the apparatus or as part of the system, as was discussed by von Neumann in work cited by the authors. With what should a theory of measurement be concerned? A broad division of approaches is defined by how one answers the question: should one try to do away with the cut between measuring apparatus and system? The authors phrase this as a choice of REFERENT, a term which in my mind puts them on shaky semantic ground; anyway The Quantum Theory of Measurement is concerned with implications of the `yes'. The book unfolds with the power of a tragedy, in which the logical consequences lead, step-by-step, to the statement and proof of theorem 6.2.1, which, roughly speaking, asserts the non-existence of a solution to the problem of getting definite pointer values from measuring apparatus that exhibits the superposition demanded by its description as a quantum system. Possible responses to this theorem are discussed, among them the many-worlds interpretation and a modification of quantum mechanics that elevates decoherence to a principle. Citations of the literature are thorough, and many points of view are crisply summarized. The book is indispensable to both those who work in the broad direction chosen by the authors and to those who wish to set any other direction in context.

Particle image velocimetry for predictions of acceleration fields and force within fluid flows

Abstract: We describe an experimental investigation of various methods of using the non-intrusive particle image velocimetry (PIV) technology to obtain the acceleration field of fluid flows and particularly the force being exchanged between a fluid flow and its boundaries. Methods based on the Lagrangian and the Eulerian specifications respectively have been developed, applied to experiments and compared. The experiments were performed by using a four-CCD-camera system designed to acquire between two and four frames in a fast time sequence, to provide single- or multiple-exposure PIV images of general fluid flows. The experiments involved various types of surface waves impinging upon a vertical wall at the end of a flume. Simultaneous monitoring with various transducers provided the experimental evaluation of the force predictions, whereas numerical simulations and PIV measurements have been used to validate the techniques for determining accelerations.

The measurement of flow velocity and acoustic particle velocity using particle-image velocimetry

Abstract: This paper outlines the method by which the flow velocity and acoustic particle velocity can be measured instantaneously over an area using particle-image velocimetry techniques. Theoretical expressions for the power spectrum and autocorrelation function of the intensity distribution in the plane of the interrogation area when a flow and sound field is present are derived and it is shown that the flow velocity and the acoustic particle velocity can be measured. The technique is used to measure the velocities in a standing wave tube with a monotonic sound field of sufficient strength such that acoustic streaming is set up. The limitations of this technique are also discussed.

Determination of the nonlinear ultrasonic parameter ? using a Michelson interferometer

Abstract: We describe an accurate optical technique for determining the nonlinear ultrasonic parameter . Our technique uses a path-stabilized Michelson laser interferometer, in contrast to more conventional methods which use piezoelectric or capacitive detectors. Features include high spatial resolution (typically ), flat bandpass response over a wide range (> 30 MHz) and simple self-calibration. We demonstrate the technique using a fused silica disc 19.15 mm thick and a fundamental frequency of 10 MHz. For comparison, was also obtained for the same specimen using capacitive and piezoelectric detectors. Errors and correction factors for all three methods are discussed; in particular, we note the importance of including ultrasonic diffraction effects. When such corrections are applied, we obtain the following results: , and . These values are in reasonable agreement with each other as well as with published values of .

Thick-film humidity sensor based on porous material

Abstract: A new compact, robust, yet fast and highly sensitive ceramic humidity sensor based on the semiconducting metal oxide has been developed using thick-film technology. The sensor element possesses a novel `sandwich' configuration with a porous ceramic layer sandwiched by two polarity-reversed interdigitated metal films. Instead of traditional glass frits, LiCl powders were used as adhesion promoters. The sintered ceramic layer exhibits a porous structure. The degree of the porosity is controlled by the amount of LiCl added and by the firing conditions for the ceramic. The surfaces of ceramic grains behave like electrolytes and easily adsorb water vapour through the pores. The novel electrode arrangement combines the advantages of humidity sensors in the form of a parallel capacitor with those in the form of an interdigital capacitor. The influence of temperature on the sensor characteristics has been compensated for by integrating a thick-film NTC resistor. The results of studies on the material processing, the fabrication and the characterization of this novel thick-film humidity sensor are described.

Chemical and Biochemical Sensing with Optical Fibers and Waveguides

Abstract: This book is a timely collection of recent results and developments in chemical and biochemical sensors based on optical planar and cylindrical waveguides. It is well known that both fields (chemical and biochemical sensing, and optical planar and fibre waveguides) are enormous as is this book. Personally I find that the book tries to cover too much in too little space. As a result, it fails to meet the expectations of readers who are attracted by its title. In order to cover as much as possible, most of the subjects dealt with in the book give large lists of references for readers to follow up. Fundamental concepts in the fields of chemical and biochemical sensing as well as optics and photonics are only briefly included so the book is not a self-contained text. Interested readers will have to follow up the related references and publications in order to master the art of a particular sensor or technology involved. Nonetheless, the book does cover the broad surface of both fields. The book is divided into four parts. Parts I and II cover the basics of chemical and biochemical sensing. The basics of optics and photonics are covered in Part III. The combination of the chemical and biochemical sensing with optics and photonics is dealt with in Part IV, which also addresses the practical sensors, sensing systems and technologies. Part I, which contains two chapters, introduces the basic concept of chemical reactions, kinetics and shape recognition, which are essential in chemical sensing. Practical sensors are used as examples to demonstrate the importance of those concepts. Part II, which contains two chapters, introduces the concepts of indicators, receptors and labels which are widely used in chemical and biochemical sensing. A few commonly used indicator compounds are described, and the technique in which these compounds are immobilized on a support is examined. Part III, which contains five chapters, briefly addresses the basic theory of optics, the concepts in optics and photonics. The optical properties of optical fibres and planar waveguides are introduced. The basic optical measurement techniques are also examined. The concepts of a few practical light sources and photodetectors are introduced. Active and passive optical components such as filters, multiplexers and polarization optical devices are briefly addressed. A brief introduction to a range of chemical and biochemical sensors is given in Part IV, which contains two chapters. The recent results of these sensors and sensing systems are reported in these chapters, some even to the point of a bulleted list with reference number. The organization of these two key chapters of the book, appears to have been rushed by the authors and no future prediction or suggestion is given on the direction in which the field should go. Readers may have to trace all references in order to see the future of this technology. This is a good introductory book for readers working in this area who are not familiar with either chemical and biochemical sensing and/or optical fibres and waveguides. Even so, fundamental concepts in the fields of chemical and biochemical sensing as well as optics and photonics are covered to a lesser depth than can be found in many undergraduate texts written for that field. For readers who are already familiar with the basic concepts in these fields, this book offers a brief summary of the recent results and developments with a large list of reference and publications for readers to follow up. In summary, this book scratches the broad surface of this field. The essential fundamental concepts, recent results and development are briefly presented. This is not a book for anyone who is interested in probing deeper into this subject. It is a book for those who wish to know a bit of everything in this field and have not yet decided whether to probe deeper into the subject. The book is fairly well presented in this regard.

Simple sensor system for measuring the dielectric properties of saline solutions

Abstract: On-line measurements of dielectric properties can be used for quality determination of process streams. Measurements of the water cut are important in order to determine how much water and oil that are e.g. produced from an oil well or how much oil is discharged to the sea. This work describes the use of a single open-ended probe measurement system for determination of the dielectric properties of saline solutions, the salinity being an important parameter in the determination of the dielectric properties of the water. The frequency range of the measurements is from 500 MHz up to 40 GHz, the salinity varying from 0 to 3.5 wt% (sea water) at C. Models are developed under controlled laboratory conditions relating the static permittivity, relaxation time and conductivity to the salinity of the water. For model verification the same set of tests are performed with a well established precision laboratory system. The potential for on-line implementation of the open-ended probe has been verified by tests in a multiphase flow loop, and these results are also presented.