G.R. Jones

Extraction of information from acoustic vibration signals using Gabor transform type devices

A technique for interpreting acoustic signals is presented based upon the use of Gabor type devices. This interpretation technique processes the information acquired from vibration sensors and presents the information as three time-varying parameters which represent the dominant signal frequency, the nominal breadth of the frequency content of the signal and its effective energy content. The technique is an extension of the chromatic analysis used successfully in the optical domain. The information produced by this analysis proves to be more convenient for defining a signal than that yielded by the conventional Fourier transform approach. By way of an example, the Gabor transform based technique is applied to the monitoring of acoustic signals generated by a high-voltage circuit breaker (as used on power transmission networks). Results are presented which indicate that the technique is capable of quantifying trends in complicated time-varying acoustical signals.

The Gabor transform basis of chromatic monitoring

Chromaticity based monitoring methodologies have evolved from polychromatic optical fibre based sensing systems, which was first implemented during the 1980s. The evolution has led to a recognition that such a methodology is applicable to monitoring systems more widely. It is shown that the method may be regarded as the manifestation of a particular form of signal representation by Gabor transforms. Examples of generically different practical implementations of the chromatic methodology to a range of different monitoring situations are given.

A fibre-optic oil condition monitor based on chromatic modulation

A novel optical fibre sensor has been developed for on-line monitoring of oil quality within industrial equipment. The monitoring is based on chromatic modulation because of the inherent self-referencing demonstrated by this technique. The sensor is shown to exhibit long-term stability and is capable of operating up to a temperature of 120 degrees C. Several industrial oils have been examined using the sensor, and typical modulation depths of 20% were obtained with resolution in the range of 0.1%. This is sufficient to record some interesting physical and chemical changes related to the reaction kinetics of oil degradation. The sensor is also capable of detecting oil leaks within a system since it can distinguish between the chromaticities of oil and air.

Sensitivity improvement of an optical current sensor with enhanced Faraday rotation

A sensitivity improvement technique is proposed for a class of bulk-glass optical current sensors that employ a ferromagnetic field concentrator. The total effective optical path length is demonstrated theoretically to be an invariant regardless of the bulk glass thickness and consequently independent of the size of the concentrator gap opening. Thus, if the magnetic field is increased by reducing the gap size, the eventual Faraday rotation for a given electric current can be increased proportionally, leading to an improved device sensitivity. The dependence of the gap magnetic field on gap size is calculated with an equivalent circuit model, and this analytical treatment is compared with a dedicated finite element computer package. By taking account of various types of optical power losses present in the bulk glass, the above formulated gap dependence of magnetic field is used to aid a realistic assessment of device sensitivity and this serves as a tool to design and analyze practical bulk-glass optical current sensors. A detailed experimental study to confirm the proposed sensitivity improvement technique is also reported.

Towards holistic chromatic intelligent monitoring of complex systems

Purpose – To introduce chromatic methods and their application to monitoring complex systems.Design/methodology/approach – Complexity is introduced and the need for holistic monitoring is suggested. The chromatic methodologies are introduced and their broad‐ranging applicability is illustrated with reference to a number of diverse applications.Findings – The generic chromatic monitoring technology has much to offer as a way of visualising, understanding, monitoring and controlling complex processes and system behaviour.Practical implications – The technology is leading to new ways of characterising and evaluating aspects of system behaviour, in a holistic and non‐intrusive manner, that are difficult to measure – e.g. walking behaviour of the elderly, tiredness of drivers.Originality/value – Draws out the generic basis of the chromatic methodology and how it may be applied to a wide range of complex systems and situations to predict when and where human intervention is required.

Chromatic signatures of broadband optical spectra for liquor discrimination

Methods based upon chromatic analysis are described for quantifying broadband optical absorption spectra in discriminating between different types of liquors. The absorption spectra are quantified by three chromaticity coordinates, which can be represented by two points, one on each of two chromatic diagrams. Various types of liquors may then be distinguished on such chromatic maps and groups of similar samples conveniently identified. Examples of the deployment of the approach are given for distinguishing between and classifying various types, brands and mixtures of alcoholic beverages and for identifying an authentic brand. The method provides a high level of traceability and is not restricted to a particular type of optical spectrum.

Diagnostic measurements on rotary arcs in hollow polymeric cylinders

Rotary arcs in hollow polymeric cylinders have been monitored using electrical and optical techniques. The arcs burning within hollow cylinders were driven by electromagnetic forces. The arc voltage, current, dielectric strength below the arc gap, the optical emissions from the chamber were measured along with high-speed photography. The diameters of the hollow cylinders and magnitude of the applied magnetic field were varied. The arc voltage, especially the extinction peak prior to current zero, increased for larger bore cylinders and higher magnetic fields. By comparing the arc voltage waveforms and arc photographs, this was shown to be because the arcs were elongated. Luminosity was detected even after current zero, when polytetrafluoroethylene was in the arc chamber. The extensive experimental results obtained have enabled empirical mathematical expressions to be derived which yield approximate indications of current interruption capabilities under different operating conditions.

Chromatic interferometry for an intelligent plasma processing system

A thin film measuring system for the online monitoring of semiconductor films during processing with a radio frequency plasma is described. The method is based upon the use of chromatic processing of polychromatic interference signals produced by the thin semiconductor film when illuminated with white light. A description is given of the interpretation of the polychromatic signals produced by interference effects and some typical experimental results are presented to illustrate the capabilities of the technique. The approach utilizes cost effective instrumentation with acceptable time response for real time process control via optical fibre transmission. It is currently being incorporated as part of an intelligent knowledge based system for such process control.

Event and movement monitoring using chromatic methodologies

An approach is presented for remotely monitoring person-based events at a series of locations in a domiciliary environment in order to extract information about movement between locations and to quantify the extent of any persistent events at a particular location. Each individual event is detected via a change in the optical chromaticity of a location and not the person. Movement between locations is determined using space and time-based chromaticity to analyse the dynamics of the sequence of events. An example of the deployment of the approach is presented.

A portable liquor monitoring system using a PC-based chromatic technique

An approach is described for discriminating between different liquors with a portable system based upon chromatic monitoring. It uses a webcam–computer combination in a robust manner and has the potential for making cursory assessments in the field. The behaviour of the system has been investigated using subsidiary measurements with a spectrometer, from which the repeatability of test results has been assessed. It is shown that the webcam–computer system can provide useful referencing to reduce the influence of system artefacts and so yield good discrimination between different liquors without the use of a spectrometer.