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Volume 147
Issue 4
IEE Proceedings - Science, Measurement and Technology
Volume 147, Issue 4, July 2000
Volumes & issues:
Volume 147, Issue 4
July 2000
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- Author(s): A.V. Nabok ; A.K. Hassan ; A.K. Ray ; J. Travis ; M. Hofton ; A. Dalley
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 153 –157
- DOI: 10.1049/ip-smt:20000461
- Type: Article
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153
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Composite Langmuir–Blodgett films of polyphenylsulphide/calix-4-resorcinarene (PPS/C-4-RA) with different molar ratios were deposited on quartz crystals and silicon wafers. Using ellipsometric and quartz-crystal microbalance methods, the thickness and mass of the film were found to increase linearly with the number of deposited layers. An optimal molar ratio for the deposition of C-4-RA/PPS films was found to be about 1/3, yielding a thickness of 9.25 nm/layer and frequency changes of 1.5 kHz/layer corresponding to surface concentration of PPS of 2 × 1022 m-2. The frequency of C-4-RA/PPS-coated quartz crystals decreases with time on exposure to ozone. Both the mass gain and concentration of oxygen appearing in the film during oxidation were calculated. The highest response was observed for LB films with the C-4-RA/PPS molar ratio of 1/3. An average ozone concentration of 0.5 ppm was recorded by QCM transducers near a standard photocopier. - Author(s): H.W. Shin ; E. Llobet ; J.W. Gardner ; E.L. Hines ; C.S. Dow
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 158 –164
- DOI: 10.1049/ip-smt:20000422
- Type: Article
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158
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An electronic nose comprising an array of six commercial odour sensors has been used to monitor not only different strains, but also the growth phase, of cyanobacteria which is normally called blue green algal. A series of experiments were carried out to analyse the nature of two closely related strains of cyanobacteria, Microcystis aeruginosa PCC 7806 that produces a toxin and PCC 7941 that does not. The authors have constructed a measurement system for the testing of the cyanobacteria in water over a period of up to 40 days. After some pre-processing to remove the variation associated with running the electronic nose in ambient air, the two different strains, and their growth phase, with principal component, were classified analysis, multilayer perceptron (MLP), learning vector quantisation (LVQ), and fuzzy ARTMAP. The optimal MLP network was found to classify correctly 97.1% of unknown non-toxic and 100% of unkhown toxic cyanobacteria. The optimal LVQ and fuzzy ARTMAP algorithms were able to classify 100% of both strains of cyanobacteria. The accuracy of MLP, LVQ and fuzzy ARTMAP algorithms with the four different growth phases of toxic cyanobacteria was 92.3%, 95.1% and 92.3%, respectively. - Author(s): F. Cecelja and W. Balachandran
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 165 –168
- DOI: 10.1049/ip-smt:20000254
- Type: Article
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165
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A high sensitivity electro-optic sensor for measurement in the near-field region has been developed and calibrated. The paper presents a theoretical analysis of the near-field measurement with particular focus on the coupling of the magnetic field. The theoretical and experimental results have been compared at a frequency of 900 MHz. The results indicate that the sensor is suitable for the near-field measurement, with the same accuracy as in the far-field region. - Author(s): V.T. Morgan ; R.D. Findlay ; S. Derrah
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 169 –171
- DOI: 10.1049/ip-smt:20000420
- Type: Article
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169
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The exact solution of the AC/DC resistance ratio of an isolated tubular conductor involves the calculation of values from 12 Kelvin functions. Previous approximate solutions are complicated, and graphical solutions require interpolation from sets of curves. A simplified solution, based on a new formula, is presented. The values of the resistance ratio derived from this formula are within ±1% of those derived from the exact solution in the practical ranges 0.05 ≤ (thickness/diameter) ≤ 0.40 and 0 < √(frequency/DC resistance) ≤ 3000, except for t/D2 = 0.40 and √(f/Rdc) > 2000. For practical tubular conductors, the formula can be used for frequencies up to about 10 kHz, depending on the thickness t and the outer diameter D2. The application of the skin effect formula to a steel-cored conductor can result in significant error.
Langmuir–Blodgett films of composite calixarene/polyphenylsulphide compounds for ozone sensing
Classification of the strain and growth phase of cyanobacteria in potable water using an electronic nose system
Validation of electro-optic sensors for near-field measurement
New formula to calculate the skin effect in isolated tubular conductors at low frequencies
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- Author(s): L.C.A. Henderson
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, page: 173 –173
- DOI: 10.1049/ip-smt:20000642
- Type: Article
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- Author(s): T.J.B.M. Janssen and A. Hartland
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 174 –176
- DOI: 10.1049/ip-smt:20000449
- Type: Article
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p.
174
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The acoustoelectric current generated by the transport of single electrons using surface acoustic waves through a one-dimensional channel offers the possibility of realising a quantum standard of current based on the electronic charge e. At NPL a measurement system using a commercial electrometer has been developed for investigating the flatness and accuracy of the constant current plateaux with an uncertainty of 15 fA. Also a new instrument, based on a cryogenic current comparator (CCC), has been developed with which it is expected that a relative accuracy of 1 fA/nA can be achieved. The authors present preliminary measurements of the quantised current using the electrometer and an experimental arrangement for resolving the ‘metrological triangle’ using the CCC. - Author(s): T.J. Witt and D. Reymann
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 177 –182
- DOI: 10.1049/ip-smt:20000414
- Type: Article
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177
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The differences between the voltage outputs of Zener-diode based electronic voltage standards (Zeners) and standard cells, between Zeners and a Josephson array voltage standard (JAVS) and between pairs of Zeners are measured. The data are analysed as time series. They are serially correlated so that the use of the usual expression for the standard deviation of the mean, the experimental standard deviation divided by the square root of the number of measurements, to characterise the dispersion is not justified. Noise in Zeners is of a 1/f nature and is characterised by using the power spectral density and Allan variance, a statistic used in time and frequency metrology. The uncertainty in the measurements of the 10 V outputs of 13 Zeners is limited by 1/f noise to a ‘floor’ value ranging between two parts in 109 and eight parts in 109 of the nominal output value. Methods are proposed for estimating the Allan variance of a Zener using either a standard cell, a JAVS, or a small group of similar Zeners. - Author(s): K. Armstrong ; J.E. Walsh ; O. Power
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 183 –185
- DOI: 10.1049/ip-smt:20000502
- Type: Article
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p.
183
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Electronic voltage standards (EVSs), based on Zener-diode reference elements, are widely used as standards to maintain a local representation of the voltage unit and as transfer standards for comparisons between local voltage reference standards at different locations. In order to make optimum use of such standards, it is important that individual units be characterised for the effects of external influence factors so that the appropriate corrections can be applied. Ambient atmospheric pressure affects the outputs of some EVSs. An experimental set-up to measure the pressure coefficient of an EVS is described and data showing the correlation between pressure and output voltage presented. Pressure coefficients calculated for the 10 V outputs of a range of commercial electronic voltage standards are also presented. - Author(s): K.K. Clarke
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 186 –189
- DOI: 10.1049/ip-smt:20000527
- Type: Article
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186
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The paper uses a set of computer controlled commercial equipment in conjunction with a software-controlled digitising voltmeter to produce accurate 100 A current measurements at ±DC and in the frequency range from 0.1 Hz to 1 kHz. Overall uncertainties in the region of ±20 ppm appear possible. The paper concentrates on 100 A results; however, the concepts work down to 10 A and up to at least 1 kA. The resultant system is nearly immune to the thermal problems and warm-up times that plague shunts and thermal convertors, particularly for currents greater than 20 A. A method to separate the transfer functions of the amplifier and the transducer is proposed. Experimental verification of the method and of the system performance is provided. - Author(s): J. Boháček
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 190 –192
- DOI: 10.1049/ip-smt:20000463
- Type: Article
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p.
190
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AC bridges developed for direct comparison of resistance or capacitance standards with quantum Hall devices are described. Owing to triple-series connection of quantum Hall devices, some of the auxiliary balance conditions are fulfilled automatically and balancing the bridges is simplified. - Author(s): S.A. Awan ; B.P. Kibble ; I.A. Robinson
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 193 –195
- DOI: 10.1049/ip-smt:20000388
- Type: Article
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A device has been constructed which permutes eleven nominally equal 50 pF capacitors in a bridge to calibrate the 10:1 and 1:10 ratios of inductive voltage dividers (IVDs) at frequencies up to 1 MHz. A compact design, which is important for high frequency measurements, was implemented using printed circuit boards and ceramic NPO dielectric capacitors. The capacitors are individually shielded to reduce errors from stray capacitances. Comparisons made with results from an existing NPL method of calibrating IVDs at frequencies up to 100 kHz and with results from a recently developed high-frequency four terminal-pair bridge show that better than 10 parts-per-million uncertainty has been attained at 1 MHz. - Author(s): M. Rodríguez
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 196 –201
- DOI: 10.1049/ip-smt:20000504
- Type: Article
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p.
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A comparison between two different methods for measurement of directivity and test port match of directional couplers and bridges is presented. One of them, the popular ripple technique, is scalar. The other method, the so-called direct calibration method as derived by Juroshek (1997), with slight differences for the simultaneous measurement of both parameters, is vectorial. The two methods make use of a vector network analyser (VNA) and the calibrations performed are verified against known standards. The uncertainty associated with both techniques is computed. - Author(s): I.J. Youngs
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 202 –208
- DOI: 10.1049/ip-smt:20000462
- Type: Article
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The complex permittivity and magnetic permeability of an artificial dielectric formed from metallised microspheres dispersed in paraffin wax are presented for wide ranges of filler volume fractions and of frequency. The measurement data are used to test the suitability of a range of simple analytical models (including effective media and percolation formalisms) for the design of ‘electromagnetically’ functional materials. The data are discussed in terms of the challenges encountered in producing reliable electromagnetic measurements on this type of material and the influence of sample preparation on the measured properties. The dilemma faced by the design engineer in selecting the appropriate blend of theory and experiment when tailoring the electromagnetic response from such a composite material is highlighted. A clear percolation transition is observed in the materials dielectric properties, and it is demonstrated that direct measurement of real permittivity near and above the percolation threshold remains a significant measurement challenge. Statistical percolation models are shown to enable an accurate fit to the measured data, although these models cannot be used to determine the percolation threshold which is simply a fitting parameter. Further evidence is provided to demonstrate the applicability of percolation theory to the material system investigated. - Author(s): P. Lederer and C. Brewitt-Taylor
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 4, p. 209 –211
- DOI: 10.1049/ip-smt:20000528
- Type: Article
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The authors have measured the microwave complex permeability in the frequency range 2–18 GHz of a series of particulate composite specimens consisting of iron particles of various sizes in the range 10–150 µm dispersed in a wax matrix at various volume loadings. The results are compared with a theoretical model based on the magnetic polarisability of a spherical conducting particle due to eddy currents induced by the incident magnetic field. They used the model to subtract the eddy current effect to reveal the fundamental ferromagnetic response of the iron and highlight the theoretical and experimental problems that arise.
Editorial: Electromagnetic measurements
Accurate measurement of currents generated by single electrons transported in a one-dimensional channel
Using power spectra and Allan variances to characterise the noise of Zener-diode voltage standards
Determination of the pressure coefficients of electronic voltage standards
100 A AC-DC current measurements to within ±25 ppm from 3 Hz to 1 kHz
AC QHE-based resistance and capacitance calibrations
Calibration of IVDs at frequencies up to 1 MHz by permuting capacitors
Comparison between the ripple technique and the direct calibration method for characterisation of directional devices
Dielectric measurements and analysis for the design of conductor/insulator artificial dielectrics
Measurement of microwave properties of magnetic particulate composites
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