Choosing the Right Instrument

Choice of equipment and experimental conditions the instrumental frequency range needs to cover the dominant relaxations of the system. It is as important to choose the temperature of the system as it is to choose the right instrument. It is also important to make the measurements over a range of conditions considerably wider than those expected in operation. 

For the spectroscopist today it is very important to choose the right method, after a cost-benefit analysis, to match the demands of the customer or serve the purpose of his research as effectively as possible. For the characterization of heterogeneous polymers a broad range of methods and instruments is available. We have tried to list the most important of them, and to emphasize their pros and cons when used for polymer imaging. 

The working principle of the thermocouple was discovered (1823) by Seebeck who observed that if wires of two different metals were joined to form a continuous circuit, a current flowed in the circuit when the two junctions were at different temperatures. In order to make a measurement, one junction (the reference junction) is maintained at a constant temperature (typically at 0°C) and the electromotive force produced when the other junction is at the test temperature is measured, or recorded, by a suitable instrument (or used as the input of a controller ). In order to choose the right kind of thermocouple among the many types available, the temperature range to be studied must be considered, as well as several requirements regarding sensitivity, calibration stability, chemical, thermal, mechanical inertia, etc. 

This chapter presents a brief and general description of electronic units used in radiation measurements. The subject is approached from the viewpoint of input-output —i.e., the input and output signals of every component unit or instrument are presented with a minimum of discussion on circuitry. The objective is to make the reader aware of the capabilities and limitations of the different types of units and, at the same time, create the capacity to choose the right component for a specific counting system. 

In research, the goal is to solve ever more difficult analytical problems, requiring flexibility in terms of methods, technical instrumentation and the researchers involved. Regulation is (still) rather low. We have to be effective, or in other words to choose the right methods from a toolbox, which is a prerequisite to reacting to a new situation in the optimal way. 

Bioreactors. Bioreactors that utilize hving cells are typically called fermenters. There are several different types of bioreactors mechanically stirred or agitated tanks bubble columns (cylindrical tanks that are not stirred but through which gas is bubbled) loop reactors, which have forced circulation packed-bed reactors membrane reactors microreactors and a variety of different types of reactors that are not easily classified (such as gas-Uquid reactors and rotating-disk reactors). Biochemical engineers must choose the best bioreactor type for the desired purpose and outfit it with the right instrumentation and other features. 

Sphere geometries vary considerably to acconunodate different instruments and specimen types. Figure 6 shows a typical example of a sphere s optical design considerations required to include or exclude a specimen s specular reflectance component. Convenient cross-tables of applications and instruments are available from some instrument companies (12, 13). Useful guides to help one choose and use the right instrument geometry to measure transmittance or reflectance of specific specimen types are available from ASTM (14). If spectral measurements must be made at angles to a specimen s surface, a standard practice is available from ASTM (15). 

More generally, when comparing different institutional frameworks (in order for instance to choose the right agricultural or food safety policy instrument) power-based considerations should accompany efficiency-based considerations. 

Available on CD, Spec Manager can be used to process multiple types of spectra. Raw data can be imported into software right from an instrument. The user can add structures and whatever additional information they choose. They can then search by SLIDE. 

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