Table of contents

The thirteenth conference in the Sensors and their Applications series took place at the University of Greenwich at Medway, Chatham Maritime, Kent in the UK from 6-8 September 2005. The event was organised by the Instrument Science and Technology Group of the Institute of Physics. Previous conferences in the series were held in Manchester (1983 & 1993), Southampton (1985 & 1998), Cambridge (1987), Canterbury (1989), Edinburgh (1991), Dublin (1995), Glasgow (1997), Cardiff (1999), London (2001) and Limerick (2003). The event provided a forum for academic researchers and industrial engineers working in all areas of sensors, instrumentation and measurement to come together to review and update themselves on the latest technical developments and applications.

The longevity of this conference series is testament to the enthusiasm and commitment from the research community working in sensors and related areas. Through presentation of oral papers, discussions at exhibited posters and informal exchanges of ideas, the conference continues to provide excellent knowledge transfer and networking opportunities. The high quality programme, headlined by notable contributions from invited speakers, included silicon microsystems, gas sensing, optical sensors, magnetic sensors, sensor networks and intelligent sensing, digital imaging and process tomography. As in previous years, this conference was particularly highlighted by a large number of sensor applications papers.

We take this opportunity to thank all of those who have contributed to the event. Our thanks also go to our colleagues in the Instrument Science and Technology Group for their support and encouragement, particularly in the refereeing of papers. Special thanks go to Claire Pantlin and her team from the Conferences Department of the Institute of Physics who have expertly managed the planning and organising of this Conference.

We hope that these conference proceedings will provide a technical insight into the development of sensors and their applications during 2005.

S J Prosser, TRW Automotive Conference Chairman Y Yan, University of Kent Local Chairman E Lewis, University of Limerick Conference Secretary

This presentation provides a personal view of some of the current trends in medical ultrasound research, with a strong emphasis on those topics where capability may be restricted by lack of availability of suitable transducers.

Loss of a natural hand means that the neural connections between the brain and the palm, fingers and thumb are also lost, including any feedback paths e.g. sensing temperature. Equipping an artificial hand with sensors allows for the inclusion of automatic control loops, freeing the user from the cognitive burden of object holding which is similar to the natural low level spinal loops that automatically compensate for object movement. Force, object slip and finger positions are variables that need to be measured in a hand designed for the physically impaired person. A high specification is required for any sensor design.

A process for batch fabrication of low-cost microcoils for magnetic resonance spectroscopy is demonstrated. Conductors are fabricated on oxidised silicon substrates by electroplating metals inside a deep photoresist mould, and passivated using an epoxy-based resist. Through-wafer deep reactive ion etching is used to define sample volumes and stencil cuts around each die, and dies are separated by snap-out. Single-coil and multiple-coil sensors are constructed by stacking parts on baseplates fabricated on the same wafer. Single turn coils have a Q-factor of ≈ 15 at 63.6 MHz, and Helmholtz coils a Q-factor of ≈ 13. Magnetic resonance imaging and spectroscopy are performed, and a SNR of 900 is achieved.

Instruments for test and calibration require a pressure sensor that is precise and stable. Market forces also dictate a move away from single measurand test equipment and, certainly in the case of pressure, away from single range equipment. A pressure `module' is required which excels in pressure measurement but is interchangble with sensors for other measurands. A communications interface for such a sensor has been specified. Instrument Digital Output Sensor (IDOS) that permits this interchanagability and allows the sensor to be inside or outside the measuring instrument.

This paper covers the design and specification of a silicon diaphragm piezo resistive SMART sensor using this interface. A brief history of instrument sensors will be given to establish the background to this development. Design choices of the silicon doping, bridge energisation method, temperature sensing, signal conversion, data processing, compensation method, communications interface will be discussed. The physical format of the `in-instrument' version will be shown and then extended to the packaging design for the external version.

Test results will show the accuracy achieved exceeds the target of 0.01%FS over a range of temperatures.

This paper describes the design of doped single crystal silicon (SCS) microhotplates for gas sensors. Resistive heaters are formed by an n+/p+ implantation into a Silicon-On-Insulator (SOI) wafer with a post-CMOS deep reactive ion etch to remove the silicon substrate. Hence they are fully compatible with CMOS technologies and allows for the integration of associated drive/detection circuitry. 2D electro-thermal models have been constructed and the results of numerical simulations using FEMLAB^® are given. Simulations show these micro-hotplates can operate at temperatures of 500°C with a drive voltage of only 5 V and a power consumption of less than 100 mW.

Existing automotive sensors do not quantify the levels of pollutants entering the atmosphere; instead they merely indicate that pollution is occurring. However to meet European legislation on emission control, it is necessary to quantify the levels of each type of pollutant leaving the exhaust of a vehicle. This paper discusses the development of an optical sensor suitable for the detection of gas emissions from a motor vehicle based on mid-infrared spectroscopy. Initial tests to detect carbon dioxide using low-cost mid-infrared components are described and a detection system, which could be fitted to an automobile, is outlined.

Inkjet printing of the conductive polymer poly(3, 4-ethylene dioxythiophene) doped with polystyrene sulfonated acid (PEDOT-PSS) has been used as the basis for a sensor for organic vapours. The electrical resistance of the film was monitored as it was exposed to atmospheres containing alcohol. Ultrathin films exhibited a sharp and nonreversible increase in their resistance. This resulted from a change in the morphology of the organic layer, thereby disrupting the current flow through the polymer. An intended application for these inkjetprinted devices is in disposable handheld instruments to monitor the presence of organic vapours above a threshold level.

In this paper we discuss results of research related to design of successive ionic layer deposition (SILD) technology for both preparing porous nano-structured SnO₂ films, and surface modification of SnO₂ films deposited by spray pyrolysis. This new method of metal oxide deposition has exited high interest, because of this method simplicity, cheapness, and ability to deposit thin nano-structured films on rough surfaces. Method of successive ionic layer deposition (SILD) consists essentially of repeated successive treatments of the conductive or dielectric substrates by solutions of various salts, which form on the substrate surface poorly soluble compounds. It was shown that SILD technology is effective method for above mentioned purposes.

The sensitivity to some reducing gases (acetone, ethanol, methane and liquefied petroleum gas-LPG) of doped nickel ferrite, Ni_0.99Co_0.01 Mn_xFe_2−xO_4−δ (x = 0.01 and 0.02), was investigated. Starting from nitrates, as raw materials, the samples were prepared by selfcombustion method. The investigations of the samples were carried out by X-ray diffraction, scanning electron microscopy and gas sensitivity measurements of the electrical resistivity. The gas sensitivity largely depends on the composition, temperature and the test gas species. Especially, the mixed ferrite with Ni_0.99Co_0.01 Mn_0.02Fe_1.98O_4−δ composition is sensitive and selective for the detection of acetone gas.

A comparison is made between conventional (i.e. uniform) and chirped optical fibre Bragg gratings (FBGs) for the detection of matrix cracking damage in composite materials. Matrix cracking damage is generally the first type of visible damage to develop under load in the off-axis plies of laminated composites and is generally the precursor of more serious damage mechanisms, particularly delamination. The detection of this type of damage is thus important, particularly in aerospace applications. Using a uniform FBG, characteristic changes develop in the reflected spectrum which can be used to identify crack development in the composite. The additional advantage of using a chirped grating is that the crack position can also be located.

Distributed measurement of pH was demonstrated at a sensitised region 4m from the distal end of a 20m length of plastic optical fibre. The cladding was removed from the fibre over 150mm and the bare core was exposed to an aqueous solution of methyl red at three values of pH, between 2.89 and 9.70. The optical fibre was interrogated at 648nm using a Luciol photon counting optical time domain reflectometer, and demonstrated that the sensing region was attenuated as a function of pH. The attenuation varied from 16.3 dB at pH 2.89 to 8.6 dB at pH 9.70; this range equated to −1.13 ± 0.04 dB/pH. It is thus possible to determine both the position to ± 12mm and pH to an estimated ± 0.5pH at the sensing region.

The evanescent radiation field associated with a suitably-prepared silica optical fibre, whereby the outer cladding has been removed and the core immersed in a liquid, has been investigated for its applicability as a device for measuring the spectral absorption of a liquid containing both chromophore and suspended scattering material. It is found that the evanescent radiation field adjacent to the core-liquid boundary interacts with chromophores in a liquid in much the same way as radiation does when directed, unbound, through a cuvette containing the same liquid in an optical spectrophotometer. However, the small penetration depth of the evanescent field, of the order of one micron, results in a sensor which is found to be insensitive to light-scattering particulate matter than was present in the liquid.

The development of a high-resolution, optical fibre Bragg grating sensor system is described that incorporates a novel digital, condition-based, phase-tracking algorithm for unwrapping the 2π phase ambiguity and permits the continuous up/down phase-tracking of multiple fringe changes. An all-fibre, Michelson interferometric phase-measurement approach is utilised for the determination of strain and temperature induced Bragg wavelength shifts. The system incorporates orthoconjugate mirrors and a stabilised reference channel to compensate for polarisation and random thermal induced drifts and has the potential for resolving sub-μstrain and mK temperature changes with a resolutions of <100n/√Hz (at 1Hz) and <10mK respectively.

The design and operating parameters of a new class of continuously distributed optical fibre sensor are described. Using counter-propagating pulses, two-photon excitation of fluorescence from ions doped into the fibre enables any position to be monitored. By this means temperature or strain may be sensed with high spatial and temporal resolution. As the doped fibre is transparent for single photon absorption at the wavelength of the light pulses, attenuation does not set an upper limit to its length.

This paper investigates detection of architectural distortion in mammographic images using support vector machine. Hausdorff dimension is used to characterise the texture feature of mammographic images. Support vector machine, a learning machine based on statistical learning theory, is trained through supervised learning to detect architectural distortion. Compared to the Radial Basis Function neural networks, SVM produced more accurate classification results in distinguishing architectural distortion abnormality from normal breast parenchyma.

This paper will present the work carried out in designing a Wireless Inertial Measurement System (WIMS) designed for a wearable system operating in an interactive dance environment. The concept underpinning this system is the generation of inertial information from multiple nodes distributed over a dancer's body, which will enable the dancer to communicate with their environment and interact with their surroundings through movement. The IMU nodes will be arranged in a network configuration whose control will be based upon existing technology developed at Tyndall.

Laser welding has been applied to various industries, in particular, automotive, aerospace and microelectronics. However, traditional off-line testing of the welds is costly and inefficient. Therefore, on-line inspection systems with low cost have being developed to increase productivity and maintain high welding quality. This paper presents the applications of acoustic, optical, visual, thermal and ultrasonic techniques and latest development of laser welding monitoring. The advantages and limitations of these techniques are also discussed.

This paper describes the development of a number of electric charge sensors. The sensors have been developed specifically to investigate triboelectric charge transfer which takes place between particles and the pipeline wall, when powdered materials are conveyed through a pipeline using air. A number of industrial applications exist for such gas–solids pipelines, including pneumatic conveyors, vacuum cleaners and dust extraction systems. The build-up of electric charge on pipelines and powdered materials can lead to electrostatic discharge and so is of interest from a safety viewpoint. The charging of powders can also adversely affect their mechanical handling characteristics and so is of interest to handling equipment engineers. The paper presents the design of the sensors, the design of the electric charge test rig and electric charge measurement test results.

A structural monitoring system has been developed for use on high value engineering structures, which is particularly suitable for use in remote locations where rare events such as accidental impacts, seismic activity or terrorist attack might otherwise go undetected.

The system comprises a low power intelligent on-site data logger and a remote analysis computer that communicate with one another using the internet and mobile telephone technology.

The analysis computer also generates e-mail alarms and maintains a web page that displays detected events in near real-time to authorised users. The application of the prototype system to pipeline monitoring is described in which the analysis of detected events is used to differentiate between impacts and pressure surges.

The system has been demonstrated successfully and is ready for deployment.

An instrumentation system is described that is capable of launching high frequency magnetic fields through a large mild steel plate 2 mm in thickness, and detecting them on the face opposite to the transmitter with remarkable signal to noise ratios. Results for signal frequencies ranging between 4.5 kHz and 13 kHz are reported. The skin depth at 9 kHz, for the steel used, is approximately 137 μm. The detection of the minute fields arriving at the receiving coil is made possible by the use of digitally synthesized input signals, low-noise amplification, and in particular the use of a real time digital signal processing system that isolates the signal of interest using a super-narrowband IIR filter and very high levels of distortion-free gain. Although traditional methods of weak signal detection, such as lock-in amplification, may also be applied in this context, the digital approach discussed here is both more cost effective and flexible, allowing the simultaneous detection of multiple frequencies.

The movement of a micrometer-size section of a single domain wall in a uniaxial garnet film was studied using a ballistic Hall micromagnetometer at 77 K and 4.2 K. The wall propagated in characteristic Barkhausen jumps, with the jump size distribution following the power-law relation, P(S) ∝ S^−τ. The scaling exponent, τ, was measured as 1.14 ± 0.05 at both temperatures. This is the first measurement of this exponent using such a device, and the first for a single wall in a two-dimensional sample with a low concentration of pinning centres, in which the magnetization of the sample is perpendicular to the surface.

The present paper is concerned with modelling the effect of decarburisation, oxidation, and the changing conductivity and permeability with carbon content and temperature in steel on the electromagnetic signal from an inductive sensor used to detect ferrite formation from austenite below the Curie temperature.

Wireless sensor networks are continuing to receive considerable research interest due, in part, to the range of possible applications. One of the greatest challenges facing researchers is in overcoming the limited network lifetime inherent in the small locally powered sensor nodes. In this paper, we propose IDEALS, a system to manage a wireless sensor network using a combination of information management, energy harvesting and energy monitoring, which we label resource awareness. Through this, IDEALS is able to extend the network lifetime for important messages, by controlling the degradation of the network to maximise information throughput.

This paper reports on the first phase deployment of bluetooth enabled condition monitoring systems at a large multinational engineering company. The radio networking of sensor signals is a fast developing area and the facilities afforded by the Wisnet device were used in the monitoring of a welding station. This and any of the planned further monitoring systems had to comply to a carefully managed IT information plan at the company. For the example application, the development and testing of microcontoller-based pre-processing of data is reported. This includes further development of the Petri Net approach to provide event-based monitoring as a sensible alternative to the continuous transmission of the sensory data.

Using the spectral selectivity and adjustable reflectivity FBGs are predestined for serial networking. Presently the addressing is realised by time division multiplex (TDM) or wavelength division multiplex (WDM). But these technologies have big disadvantages regarding the effective use of the prevailing resources time and wavelength, respectively. In this paper a new scheme capable of addressing a large number of FBGs in a single serial network is proposed and compared to TDM and WDM. Using all optical sequence inversion keyed (SIK) direct sequence (DS) code division multiplex (CDM) it overcomes the restrictions handling the resources time and wavelength without losing accuracy.

Designating a sensor as intelligent is a long-standing term implying that it provides more functionality than merely providing an output measurement. Since there is some discrepancy governing what makes a given sensor intelligent, this paper defines the features required for improving confidence in sensor measurements, from the sensor management perspective. We describe a software framework used to implement tasks such as condition monitoring onboard the sensor itself, rather than at the traditional supervisory level. The algorithms include data-based models, which allows for modelling of non-linear effects and estimation uncertainty, which is a prerequisite for data fusion. Density estimation for novelty detection is demonstrated for an accelerometer that is purposely damaged in an environmental chamber.

A novel on-line monitoring technique for a range of MEMS and integrated sensor systems is presented based on the injection of a test stimuli into the bias structure of transducer functions. The technique `Bias Superposition' utilises both signal injection and signal extraction techniques to achieve an indication of structural integrity of the transducer and interface. The technique has been successfully applied to a thick film conductance sensor.

This paper presents an algorithm for the three-dimensional (3D) visualisation and luminosity reconstruction of a combustion flame. A combination of image processing techniques and filtered-back projection algorithms is employed to reconstruct grey-scale sections of the flame from three 2D images taken by three identical CCD monochromatic cameras placed around the flame. The technique proposed is capable of reconstructing both cross- and longitudinal sections of the flame, and consequently a complete 3D luminous model of the flame.

The development and application of a charge-coupled device (CCD) sensor for neutron detection is described. The sensor provides images of neutron-induced single-event effects (SEEs) at 9 μm pixel resolution and a charge/pixel resolution of typically 36.6 electronic charges. Example results are presented, showing the charge profiles resulting from single events observed during tests in a representative neutron spectrum. The sensor enables aspects of SEE phenomena to be studied directly in more detail than hitherto.

This paper presents an investigation into the suitability of imaging based sensors to measure particle shape and the effects of shape size on measurement consistency, testing the often used assumption that imaging based particle size analysers are insensitive to changes in particle shape. The imaging system employed is introduced and the definitions of shape used here are explained. A number of varying shaped `particles', in the form of static test images, are observed with the imaging system and the effect of varying shape size on the resulting measurements is investigated. In general the results suggest that reliable shape measurement is possible but that the effects of image quantisation do lead to variations in measured quantities under real-world conditions.

Electrical capacitance tomography (ECT) is an effective technique for elucidating the distribution of dielectric materials inside closed pipes or vessels. This paper describes a virtual electrical capacitance tomography (VECT) system, which can simulate a range of sensor and hardware configurations and material distributions. A selection of popular image reconstruction algorithms has been made available and image error and capacitance error tools enable their performance to be evaluated and compared. Series of frame-by-frame results can be stored for simulating real-time dynamic flows. The system is programmed in Matlab with DOS functions. It is convenient to use and low-cost to operate, providing an effective tool for engineering experiment.

An optical fibre based sensor has been developed to aid the quality assurance of food cooked in industrial ovens by monitoring the product in situ as it cooks. The sensor measures the product colour as it cooks by examining the reflected visible light from the surface as well as the core of the product. This paper examines the use of the sensor for the detection of blood in the spinal area of cooked whole chickens. The results presented here show that the sensor can be successfully used for this purpose.

With the advent of digital imaging and image processing techniques vision based monitoring and characterisation of combustion flames have developed rapidly in recent years. This paper presents a short review of the latest developments in this area. The techniques covered in this review are classified into two main categories: two-dimensional (2D) and 3D imaging techniques. Experimental results obtained on both laboratory- and industrial-scale combustion rigs are presented. Future developments in this area also included.

This paper describes the first use of novel blue diode lasers to make temperature measurements based on fluorescence. As a demonstration of this principle, indium atoms were seeded as a probe species into flames and the resulting diode laser induced fluorescence allowed an accurate determination of the temperature at a point. This permits spatially resolved measurements to be made, which are impossible to achieve using the established absorption based sensors. The technique opens up a range of application possibilities in dynamic and inhomogeneous reacting flows.

Advanced electromagnetic sensor systems more commonly associated with the hightech military battlefield may be applied to remote surveillance of wildlife. The first comprehensive study of a wide global variety of Near Infra Red (NIR) and thermal wildlife portraits are presented with this technology: for mammals, birds and other animals. The paper illustrates the safety aspects afforded to zoo staff and personnel in the wild during the day and night from potentially lethal and aggressive animals, and those difficult to approach normally. Such remote sensing systems are non-invasive and provide minimal disruption and distress to animals both in captivity and in the wild. We present some of the veterinarian advantages of such all weather day and night systems to identify sickness and injuries at an early diagnostic stage, as well as age related effects and mammalian cancer. Animals have very different textured surfaces, reflective and emissive properties in the NIR and thermal bands than when compared with the visible spectrum. Some surface features may offer biomimetic materials design advantages.

The use of optical fibres for the measurement of ozone based on the optical absorption of both UV light at 254nm and visible light at 600nm is investigated and tested. Calculations based on the Beer-Lambert Law are also presented to demonstrate the high resolution of the UV based sensor in determining the concentration of ozone in the range of 0 mg/litre to 1mg/litre and the ability of the visible based sensor to measure high concentrations over a wide range.

Coronas are partial discharges that occur in regions of non-uniform electric fields adjacent to conductors stressed to high voltages. Negative, Trichel-pulse coronas in air occur when a dc, negative-polarity, high voltage is applied to a conductor. Trichel pulses in atmospheric air generate significant amounts of ozone as well as electrical and acoustic noise. Under the right conditions these coronas can be a precursor to complete electrical breakdown of the air gap due to a reduction in the density of neutral molecules resulting from a combination of localised heating and convective air flow generated by the movement of negative ions. An optical fibre anemometer, based on a Mach-Zehnder interferometer has been constructed to measure the speed of the wind generated in the point-plane gap of a negative, Trichel-pulse corona discharge in atmospheric air. The sensing arm of the fibre interferometer is subjected to controlled, repetitive bursts of infrared radiation from a CO₂ laser and the combination of localised heating and convective cooling by the corona wind results in fringe shifts which are directly calibrated to the speed of the wind. This paper reports on the nature of the calibration process and presents some radial profiles of wind speed in the corona gap.

We describe miniature all-optical pressure sensors, fabricated by wafer etching techniques, less than 1mm² in overall cross-section with rise times in the μs regime and pressure ranges typically 600 kPa. Their performance is suitable for experimental studies of the pressure-time history for test models exposed to shocks initiated by an explosive charge. The small size and fast response of the sensors promises higher quality data than has been previously available from conventional electrical sensors, with potential improvements to numerical models of blast effects. Provisional results from blast tests will be presented in which up to 6 sensors were multiplexed, embedded within test models in a range of orientations relative to the shock front.

A novel fibre optic sensor system has been developed to enable the linear location of acoustic emission. The demonstration of linear location of acoustic emission was conducted using a pair of serial multiplexed fibre coupler-based acoustic emission (AE) sensors in conjunction with a single light source. The simulated AE source, via a pencil lead-break test, was located to within ± 5mm.

An optical fibre sensor capable of detecting various concentrations of ethanol in water supplies is reported. The sensor is based on a U-bend sensor configuration and is incorporated into a 170-metre length of silica cladding silica core optical fibre. The sensor is interrogated using Optical Time Domain Reflectometry (OTDR) and it is proposed to apply artificial neural network (ANN) pattern recognition techniques to the resulting OTDR signals to accurately classify the sensor test conditions. It is also proposed that additional U-bend configuration sensors will be added to the fibre measurement length, in order to implement a multipoint optical fibre sensor system.

Increasingly, the need to seamlessly link high-level behavioural descriptions of electronic hardware for modelling and simulation purposes to the final application hardware highlights the gap between the high-level behavioural descriptions of the required circuit functionality (considering here digital logic) in commonly used mathematical modelling tools, and the hardware description languages such as VHDL and Verilog-HDL. In this paper, the linking of a MATLAB^® model for digital algorithm for implementation on a programmable logic device for design synthesis from the MATLAB^® model into VHDL is discussed. This VHDL model is itself synthesised and downloaded to the target Field Programmable Gate Array, for normal operation and also for design debug purposes. To demonstrate this, a circuit architecture mapped from a SIMULINK^® model is presented. The rationale is for a seamless interface between the initial algorithm development and the target hardware, enabling the hardware to be debugged and compared to the simulated model from a single interface for use with by a non-expert in the programmable logic and hardware description language use.

This paper describes an optical fibre near infrared Carbon Dioxide sensor. Using an integrating sphere as a test cell, increased path length is achieved due to multiple reflections within the sphere. Carbon dioxide is input into the sphere via an unused optical port. Light from a C + L band ASE source is transmitted through the sphere and any absorption is detected using a near infrared spectrometer. A change in optical intensity was observed at a wavelength of 1.59 um when carbon dioxide was present from which the carbon dioxide concentration can be determined.

The different methods of structural engineering, used for improvement of solid state gas sensors parameters are reviewed in this paper. The wide possibilities of structural engineering in optimization of gas sensing properties were demonstrated on the example of thin tin dioxide films deposited by spray pyrolysis.

Polymethylmethacrylate (PMMA) optical fibres are low-cost polymer fibres that are generally more physically robust than silica fibres, are more flexible, yet like silica fibres have the potential to be used for practical evanescent field absorption sensors in aqueous solutions. However, evanescent field absorption in aqueous solutions is influenced by more than just the specific absorptivity of the solution in question. The physical configuration of the optical fibre itself, as well as surface charge interactions between the fibre and the chromophore in the solution also significantly affects the sensitivity of the fibre to evanescent field absorption. This paper reports on an investigation of numerous physical phenomena that influence evanescent field absorption for PMMA fibres using an aqueous solution of the dye Amidoblack. Parameters investigated included fibre coiling configuration and bend radius, fibre interaction length, and effect of solution pH. Coiled fibres were found to be more sensitive to evanescent field absorption than straight (uncoiled) lengths, and sensitivity was found to increase with a further reduction in bend radius. At high solution pH, the absorption versus solution concentration proved to be linear whereas at low pH the absorption versus concentration relationship exhibited a clear deviation from linearity. The observed nonlinearity at low pH points to the importance of accounting for electrostatic interactions between chromophore and fibre surface when designing a PMMA sensor for evanescent field absorption measurements in aqueous solutions.

Observations of axial acoustic waves in multimode polymethylmethacrylate (PMMA) optical fibres are reported. Rapid electrostriction was induced in a 1.25 m length of PMMA optical fibre using a pulsed transverse electric field of ∼10⁶ V m⁻¹. By observing the effects of birefringence on a polarised laser beam, acoustic waves travelling with a speed of 1050 m s⁻¹ were observed to travel between the fibre ends. Simple calculations indicate that these acoustic waves comprised shear waves, although propagation of surface waves could not be ruled out. The implications of these observations in terms of a new class of optical fibre sensors based on the propagation of axial acoustic waves are also discussed.

A novel sensor structure of electromagnetic tomography system is presented in this paper. Flexible circuit straps are used in the excitation layer of the sensor and current of each strip can be controlled independently according to the excitation protocol matrix. In the sensor three kinds of excitation protocols: parallel, quasi-parallel and coil pair can be generated. Furthermore excitation field simulation and image reconstruction experiments have been done for analyzing the performance of the different excitation protocols.

In this paper, a virtual instrument network through the LAN and finally remote control of virtual instruments is realized based on virtual instrument and LabWindows/CVI software platform. The virtual instrument network system is made up of three subsystems. There are server subsystem, telnet client subsystem and local instrument control subsystem. This paper introduced virtual instrument network structure in detail based on LabWindows. Application procedure design of virtual instrument network communication, the Client/the programming mode of the server, remote PC and server communication far realizing, the control power of the workstation is transmitted, server program and so on essential technical were introduced. And virtual instruments network may connect to entire Internet on. Above-mentioned technology, through measuring the application in the electronic measurement virtual instrument network that is already built up, has verified the actual using value of the technology. Experiment and application validate that this design is resultful.

In this aperture synthesis three snapshots are required to synthesis the aperture: one is obtained with simple illumination of the scene, the second when the scene is projected with cosine fringes and the third with the fringes quadrature phase shifted. The spatial frequency of the fringes is set to twice the cut off frequency of the imager. Due to spatial frequency heterodyning bands of scene spatial frequencies lying both above and below the fringe spatial frequency are heterodyned simultaneously into the low-pass band of the imager. Computer simulation results show extension of cut off frequency of the imager to three times the cut off frequency without aperture synthesis.

The micostructure and humidity sensitivity of MgFe₂O₄ + CaO, Mg_0.5Cu_0.5Fe_1.8Ga_0.2O₄, Mg_0.5Zn_0.5Fe₂O₄ + KCl and MgMn_0.2Fe_1.8O₄ ferrites were investigated. We have found that the humidity sensitivity largely depends on composition, crystallite size, surface area and porosity. The best results concerning humidity sensitivity were obtained for MgMn_0.2Fe_1.8O₄ ferrite.

Electromagnetic (EM) solenoid actuators are widely used in many applications such as the automobile, aerospace, printing and food industries where repetitive, often high-speed linear or rotating motions are required. In some of these applications they are used as highspeed `switching' valves for switching pneumatic channels. This paper describes the finite element (FE) modelling and design of high-speed solenoid actuators. Operating at frequencies between 150–300 Hz, these actuators are unique in terms of the large force they produce (8–15 N) and the requirement for very long lifetime (2-5 billion cycles). The complex nature of electromagnetic, motional and thermal problems is discussed. The methodologies for FE modelling of such high-performance actuators are developed and discussed. These are used for modelling, design, performance evaluation and prediction of the above high-speed actuators. Modelling results showing some of the key design features of the actuators are presented in terms of force produced as a function of various design parameters.

This paper is a description of the development of an embedded controller for high power industrial diesel generators. The aim of the project was to replace the existing discrete logic design by an intelligent versatile and user configurable control system. A prototype embedded PC controlled system was developed, capable of fully replacing the existing system, with a colour TFT display and keypad. Features include fully automatic generator control as before with status and alarm display and monitoring of engine parameters, along with data logging, remote communications and a means of analysing data. The unit was tested on the bench and on diesel generators for the core controlling functionality to prove compliance with the specifications. The results of the testing proved the unit's suitability as a replacement for the existing system in its intended environment. The significance of this study is that a low cost replacement solution has been found for an industrial application by transferring modern technological knowledge to a small business. The company are now able to build on the design and take it into production, reducing servicing and production costs.

In order to detecting the magnetic leakage fields of the wire rope defaults, a transducer made up of the fluxgate array is designed, and a series of the characteristic values of wire rope defaults signals are defined. By processing the characteristic signals, the LF or LMA of wire rope are distinguished, and the default extent is estimated. The experiment results of the new method for detecting the wire rope faults are introduced.

A fluorescence-based temperature sensor system using a digital signal processing approach has been developed and evaluated in operation on a working automotive engine. The signal processing approach, using the least squares method, makes the system relatively insensitive to intensity variations in the probe and thus provides more precise measurements when compared to a previous system designed using analogue phase-locked detection. Experiments carried out to determine the emission temperatures of a running car engine have demonstrated the effectiveness of the sensor system in monitoring exhaust temperatures up to 250°C, and potentially higher.