Ultrasonic measurement techniques

Table 1. Three different ultrasonic measuring techniques for thickness measurement.

Ultrasonic measurement techniques applicable to food emulsions are reviewed extensively elsewhere (11—15) and only a brief introduction is presented here. Most ultrasonic measirrement systems require an electrical signal generator that is used to excite an ultrasonic transducer to produce an acoustic wave which, after passing through the emulsion, is detected by a second transducer (or the first after a reflection). Finally, a display system, usually a computer or oscilloscope, is used to record and store the elec-... 

The three basic ultrasonic measurement techniques most widely used today are ... 

Figure 18-6. Thickness tester, using ultrasonic measurement technique. (Courtesy of Panametrics Corporation.)...

Chai, G.-Y., Greenberg, A. R., and Krantz, W. B. (2003). Study of using in-situ ultrasonic measurement technique in membrane separation. J. Membr. Set Technol. (China) 23, 135. 

L.C. Lynworth, Ultrasonic Measurements for Process Control Theory, Techniques, Applications, Academic Press, New York, NY (1989). 

The objectives of this chapter are to introduce the basic concepts of ultrasonic propagation in materials, to describe some of the most important methods for measuring and interpreting ultrasonic measurements, and to outline existing and possible applications of the technique in the food industry. 

Continuous wave methods are the most accurate means of making ultrasonic measurements. Even so, they are used less frequently than pulse methods because measurements are more time consuming and laborious to carry out, are more difficult to automate, and the measurement cell requires a high degree of precision engineering. These techniques therefore tend to be used in specialized research laboratories where accurate measurements are important. Continuous wave ultrasound is utilized in a variety of different techniques, but the most commonly used is the interferometer [10,11]. 

L.C. Lynworth, Ultrasonic measurements for process control theory, techniques, applications, Academic Press, San Diego, 1989. 

Although the effect of the concentration of suspension on the results of the measurement of pigments has never been proven, the development of techniques able to cope with concentrations closer to the applications if of interest These would make it possible, for example, to determine the particle size distribution in a dispersion paint or in a reaction vessel where a pigment is produced by the precipitation process. A measurement technique having no problems, in principle, with high concentration dispersions is the scattering of ultrasonic waves. Nevertheless the instruments on the market have up to now failed to realize the great expectations of this technique. 

Notwithstanding its significant potential for high-resolution ultrasonic measurements in the analysis of liquids, this technique has for a long time been used mainly by professional ultrasonic laboratories. More widespread use of US for liquid monitoring and analysis has been limited by hindrances such as the following ... 

Measurement of the relative energies of twist and chair conformations is possible using ultrasonic relaxation techniques which are suitable for observing equilibria in which there is as little as 0.1% of the higher energy conformer. By combining results from this technique with the earUer nmr... 

However, laser diffiaction can only be used as an off-line measurement technique, as it requires relatively low particle concentrations. In contrast to it, ultrasonic spectroscopy can be applied as an on-line technique, but the sensitivity towards coarse particles is not as high as for laser diffraction (Fig. 6). 

Ultrasonic interferometry, in which the travel time of high-frequency elastic waves through a sample is measured, also yields elastic moduli. Because it is a physical property measurement, rather than an optical spectroscopy, it can be used equally well on poly-crystalline samples as single-crystals, although polycrystalline measurements only yield the bulk elastic properties, bulk modulus and shear modulus, G. High-pressure ultrasonic interferometry techniques were initially developed in the piston cylinder... 

GBC Scientific Equipment offers a Micro Fourier Rheometer, MFR 2100. The rheometer applies a squeezing motion to the sample, performing analyses on sample volumes less than 100 p.1. An automated sample injection system is included in the instrument design. The rheometer is capable of handling low-viscosity fluids, 1 mPas, with storage modulus measurement down to 10-4 Pa. Using a different measurement technique, both benchtop and in-line, the real-time ultrasonic rheometer and fluid characterization device uses spatially resolved ultrasonic... 

Studies of the phase equilibria (determined by the diverse scattering methods, viz. turbidity, PICS, SAXS, SANS, by fluorescence techniques, ultrasonic measurements, etc.). 

Ultrasonic relaxation techniques have been used to estimate the energy barrier to syn-anti conformational interconversion in cytidine 2, 3 -mono-phosphate, in the presence and absence of ethidium bromide. Raman spectroscopic measurements on a number of dinucleoside monophosphate crystals of precisely known sugar-phosphate structure have been compared with those of B- and A-form DNA, to give information on the comparative rigidity of the backbone in the nucleic acids. The same technique, applied to poly(dA-dT) and poly[d(A-T)] at different temperatures, suggests that some of the furanose... 

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