Direct-reading Measurement Techniques

Direct-reading Measurement Techniques 6.9.3.1 Tubes with Direct Indication... 

Chemical measurements can be performed during developing stages of fire using direct reading measurements and sampling techniques like sorbent tubes. 

Ultrasonic Microhardness. A new microhardness test using ultrasonic vibrations has been developed and offers some advantages over conventional microhardness tests that rely on physical measurement of the remaining indentation size (6). The ultrasonic method uses the DPH diamond indenter under a constant load of 7.8 N (800 gf) or less. The hardness number is derived from a comparison of the natural frequency of the diamond indenter when free or loaded. Knowledge of the modulus of elasticity of the material under test and a smooth surface finish is required. The technique is fast and direct-reading, making it useful for production testing of similarly shaped parts. 

Optical read out will compete with micro electrode arrays. New developments in array detectors will open new perspectives. Direct optical detection techniques will add new possibilities to bioanalytical applications in addition to fluorescence measurements presently preferred in biochips read out. 

Baron, P. A., M. K. Mazumder, and Y. S. Cheng, Direct-Reading Techniques Using Optical Particle Detection, in Aerosol Measurement Principles, Techniques, and Applications (K. Willeke and P. A. Baron, Eds.), pp. 381-409, Van Nostrand Reinhold, New York, 1993. 

In chemistry, calibration has a special place because direct measurement of concentrations is rarely possible. The only direct concentration determination used is the cumbersome technique of gravimetry. For simple binary mixtures, density, refractive index, conductivity, polarization angle etc. may be used for measuring concentration. This is almost a direct chemical measurement because the concentration can be read out of a table. This principle is used, for instance, in measuring the H2SO4 concentration of battery acid by density measurement. 

A variety of sampling techniques has been tried for measuring organic vapors in exhaled air. Table 15.2.1.1 shows a classification of these techniques. The main distinction is between direct reading instruments and transportable samples that require analysis in the laboratory. The former group covers the widest range, from simple detector tubes to High Resolution Mass Spectrometry. 

D. J. Rader and T. J. O Hern. Optical Direct Reading Techniques In Situ Sensing. n Aerosol Measurement Principles, Techniques, and Applications. 

Solvents are measured with various techniques and instrumentation. A brief overview of the direct-reading field instrumentation and other sampling techniques for solvents and their laboratory analyses follows (McEee 1988). 

Separation techniques may have to be applied if the given sample contains substances which act as interferences (Section 21.10), or, as explained above, if the concentration of the element to be determined in the test solution is too low to give satisfactory absorbance readings. As already indicated (Section 21.10), the separation methods most commonly used in conjunction with flame spectrophotometric methods are solvent extraction (see Chapter 6) and ion exchange (Chapter 7). When a solvent extraction method is used, it may happen that the element to be determined is extracted into an organic solvent, and as discussed above it may be possible to use this solution directly for the flame photometric measurement. 

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