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Background Principles and Measurement Modes

The bottom- and side-loading thermobalances shown in Figs. 3.2a and 3.2b utilize conventional resistive heating elements, while the bottom-loading example selected in Fig. 3.2c utilizes radiant heating elements necessitating a transparent tube to constrain the atmospheric flow. [Pg.242]

Electrostatic and magnetic forces Sample-furnace-sensor arrangement [Pg.244]

One approach to compensate for buoyancy and general baseline issues encountered with very small mass loss is to perform a second experiment with a closely matching inert sample and subsequently subtracting this blank experiment. A series of such experiments can be stored for future use. An excellent example of this technique was the determination of the coating thickness on fused-silica fibers (Gallagher 1992). Fibers were initially heated in an oxidizing atmosphere to burn off the very thin polymer coating. They were [Pg.244]

All thermobalances effectively utilize baffling to reduce the thermal convection currents that would otherwise disturb the measurement of mass and heat the balance compartment. Optimization of the atmospheric flow pattern and the baffling are critical to reduction of thermal noise and drift in the measurement of the mass. Many models will impose a water-cooled plate between the balance compartment and the furnace. When long-term stability is required, it is advisable to consider actually thermostatting the balance compartment. Since heat normally rises, vertical configurations are most susceptible. The horizontal arrangement leads to less interference from the flow patterns arising from control of the atmosphere. [Pg.245]

Clearly it is essential that the sample, any volatile species, and any reactive atmosphere not react with the sample holder or other components with which they may come in contact. This is seldom an issue with polymers however, the interaction of phosphorous containing polymers with platinum above 900 °C is one exception. Condensation of volatile products on the suspension in cooler portions of the furnace may be avoided by using a sufficient gas flow or longer hot zone. The flow pattern of the atmosphere, the baffling, and the thermobalance configuration all affect the likelihood of such a problem. [Pg.245]


By repeating this measurement mode several to hundreds times for accumulation, remarkably high S/N ratios are obtained. The principle enables the measurement of very small signals, which are embedded in the background signal and could not be measured in the normal fluorescence measurement, and thus gives remarkably high sensitivity with very low detection limit. In the authors laboratory, several proteins were measured in serum for the first time with this method. These will be introduced in a later section. This method is especially effec-... [Pg.190]

In this chapter we present background principles of thermogravimetric analysis and the various measurement modes issues associated with and recommendations for calibration measurement and analysis methods for characterizing polymeric materials, including recommendations for how to perform a TGA experiment and kinetics. At the end of the chapter we present selected applications of actual industrial problems where TGA has been instrumental in their solution. [Pg.242]

There are limits on this method which are imposed by the la e pacing of laser mode-noise peaks (130 MKz), setting an upper decay time limit of 7 ns, by detector noise background setting a lower Ifanit of 200 ps, of cost (of a spectrum analyser) and of difficulties in analysis of multi-component fluorescence. Since however any source could in principle be used to measure a noise spectmm, the method is worth further consideration. [Pg.89]


See other pages where Background Principles and Measurement Modes is mentioned: [Pg.242]    [Pg.243]    [Pg.245]    [Pg.247]    [Pg.249]    [Pg.242]    [Pg.243]    [Pg.245]    [Pg.247]    [Pg.249]    [Pg.771]    [Pg.38]    [Pg.175]    [Pg.225]    [Pg.433]    [Pg.593]    [Pg.444]    [Pg.776]    [Pg.175]    [Pg.900]    [Pg.495]    [Pg.361]    [Pg.142]    [Pg.473]    [Pg.958]    [Pg.520]    [Pg.459]    [Pg.89]    [Pg.247]    [Pg.287]   


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Measurement modes

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