INSTRUMENTS AND MEASUREMENTS

The D Arsonval galvanometer plays a very important role in electrical measurements. A coil of wire located in a magnetic field produced by permanent magnets is mounted on low friction bearings (Fig. 10.14). Rotation is constrained by coil springs that also conduct current to and from the coil. A pointer attached to the coil moves across a scale that indicates rotary displacement proportional to the current (/), flowing through the coil. 

In the case of Fig. 10.15 (b) a shunt of large resistance (R) is in parallel with the small internal resistance of the galvanometer (r). The current in the external circuit from yl to 5 in Fig. 10.15 (b) will then be  

By use of a wide range of resistances, R in Fig. 10.15, a very sensitive galvanometer may be capable of measuring a wide range of voltages and currents. 

The Wheatstone bridge (Fig. 10.16) is a convenient means for measuring small values of resistance. No current will flow through the galvanometer (G) if  

Let7 2 andi 3 be fixed precision resistances,i i a variable resistance, andi 4 an unknown resistance. Then the variable resistance may be adjusted until no current flows through the galvanometer. The three known resistances may be substituted into Eq. (10.27), and the unknown resistance R determined. The resistance may then be read from a scale on a selfbalancing potentiometer, an instrument that balances automatically. 

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P.Mas, P Delmotte, P. Sas, Proc. of IEEE Instrumentation and Measurement Technology Conference Brussels, June 4-6, 1996. 

The combination of non-ideal phase behaviour of solutions, the non-linearity of particle formation kinetics, the multi-dimensionality of crystals, their interactions and difficulties of modelling, instrumentation and measurement have conspired to make crystallizer control a formidable engineering challenge. Various aspects of achieving control of crystallizers have been reviewed by Rawlings etal. (1993) and Rohani (2001), respectively. 

Identify the test instrumentation and measurement procedures, schedules, etc, that are required for a fully specified test design ... 

High-performance instruments and measurements of unprecedented precision, sensitivity, spatial resolution, or specificity ... 

Low-cost, robust instruments and measurements for monitoring and analyzing exceptionally small volumes, for real-time control of pro-... 

M. Lazzaroni, E. Pezzotta, G. Mendu-ni, D. Bocchiola, D. Ward, conference records of the 17 IEEE Instrumentation and Measurement Technology Conference Smart Connectivity Integrating... 

Fluorescence Instrumentation and Measurements. Fluorescence spectra of the FS samples were obtained on a steady state spectrofluorometer of modular construction with a 1000 W xenon arc lamp and tandem quarter meter excitation monochromator and quarter meter analysis monochromator. The diffraction gratings In the excitation monochromators have blaze angles that allow maximum light transmission at a wavelength of 240 nm. Uncorrected spectra were taken under front-face Illumination with exciting light at 260 nm. Monomer fluorescence was measured at 280 nm and exclmer fluorescence was measured at 330 nm, where there Is no overlap of exclmer and monomer bands. 

Rul] W. R. Runyan, Semiconductor Instrumentation and Measurements, McGraw-Hill, New York, 1975, Chapter 4. 

As noted in the last section, the correct answer to an analysis is usually not known in advance. So the key question becomes How can a laboratory be absolutely sure that the result it is reporting is accurate First, the bias, if any, of a method must be determined and the method must be validated as mentioned in the last section (see also Section 5.6). Besides periodically checking to be sure that all instruments and measuring devices are calibrated and functioning properly, and besides assuring that the sample on which the work was performed truly represents the entire bulk system (in other words, besides making certain the work performed is free of avoidable error), the analyst relies on the precision of a series of measurements or analysis results to be the indicator of accuracy. If a series of tests all provide the same or nearly the same result, and that result is free of bias or compensated for bias, it is taken to be an accurate answer. Obviously, what degree of precision is required and how to deal with the data in order to have the confidence that is needed or wanted are important questions. The answer lies in the use of statistics. Statistical methods take a look at the series of measurements that are the data, provide some mathematical indication of the precision, and reject or retain outliers, or suspect data values, based on predetermined limits. 

Nelson, S., Stetson, L. and Schlaphoff, C. 1974. A general computer program for the precise calculation of dielectric properties from short circuited waveguide measurements. IEEE Transactions on Instrumentation and Measurement 23(4) 455-460. 

Stuchley M. and Stuchley S. 1980. Coaxial line reflection methods for measuring dielectric properties of biological substances at radio and microwave frequencies — a review. IEEE Transactions on Instrumentation and Measurement. 29(3) 176-183. 

A project at Amoco was undertaken to verify his NIR results and turn the instrument and measurement into something that could be used on-line. At first, there was total failure at duplicating his results with the precision that was needed to be useful. Then, the samples were split by gasoline grade and the results improved dramatically. When the sample sets were split by both grade and refinery it became clear that a very useful correlation between all three octane numbers and the NIR spectra could be constructed for specific grades and refineries. 

Compared to the simplicity of the relative method, with its simple measurement equation, there is a hidden complexity in the k0 method complex algorithms, dedicated software for reactor neutron fluxes and gamma ray measurement efficiency and many problems associated with spectrum deconvolution. The method relies on a complex set of written standards which are not always fully understood by the average user. It uses non-transparent instrumentation and measurement processes. In short the method becomes, forgive the terminology, non-traceable to the user and this is, I believe, worse than non-traceable to SI units. 

Many analytical methods (Examples 2 and 4) cannot be directly or indirectly linked to Si-units with any of the available primary methods of measurement. These can only be used in exceptional cases for a limited range of rather simple problems. Hence, many methods of analysis rely on other methods for the assessment of their accuracy. The instrumentation and measurement process used must be transparent and a full account of sources of error, relative and absolute, must be made. Unfortunately, as Examples 2 and 3 show, with the growing complexity of analytical methods this transparency becomes a major headache for both metrologists and analytical chemists. The relationship between signals measured and the derived concentration becomes a complex calculation [6] and the result of a measurement in many methods can only be traceable to the instrument, its electronics and integrated software [33],... 

Yin, W. L., and Wang, H. X., Quantification of swirling flow in hydraulic conveying from resistance tomography images, Instrumentation and Measurement Technology Conference (Conference Proceedings, Vail, CO, USA), 20-22 May (2003). 

Hogan T, Taylor S, Cheung K, Velasquez-Garcia L, Akinwande A, Pedder R (2010) Performance Characteristics of a MEMS Quadrupole Mass Filter With Square Electrodes Experimental and Simulated Results. IEEE Transactions on Instrumentation and Measurement 59(9) 2458-2467... 

We present the basic concepts and methods for the measurement of infrared and Raman vibrational optical activity (VOA). These two forms of VOA are referred to as infrared vibrational circular dichroism (VCD) and Raman optical activity (ROA), respectively The principal aim of the article is to provide detailed descriptions of the instrumentation and measurement methods associated with VCD and ROA in general, and Fourier transform VCD and multichannel CCD ROA, in particular. Although VCD and ROA are closely related spectroscopic techniques, the instrumentation and measurement techniques differ markedly. These two forms of VOA will be compared and the reasons behinds their differences, now and in the future, will be explored. 

Since 1958, an extensive experimental literature has developed, primarily on epoxies, and, to a lesser extent, on polyesters, polyimides, phenolics, and other resins. Work in this area has been greatly stimulated by the increasing importance of thermosets as matrix resins in fiber reinforced composites, and by significant improvements in instrumentation and measurement methods. 

See for example the Journals Review of Scientific Instruments and Measurement Science and... 

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