Measurement of static charges

The measurement of static charge on textile fibers, fabrics, and yams has also received a considerable amount of scientific attention and is relevant to this same subject on human hair. The books by Meredith and Hearle [141] and Morton and Hearle [136] provide a good introduction into this subject. The measurement of electrical resistance (reciprocal of conductance) of fibers is also fundamental to their static electrification and is described by Hersh [142] for human hair and other fibers and by Meredith and Hearle [141] for textile fibers. 

The active pharmaceutical ingredient in a low-dose formulation is typically a small molecule, designed to meet a small particle size requirement for uniformity purposes, and can be susceptible to effects of static charge and segregation. The impact of static charge on the accuracy of blend uniformity measurements (i.e., sampling bias) is discussed in the next section. 

Use Radiation source in industrial thickness gauges, elimination of static charge, treatment of eye diseases, in radio-autography to determine the uniformity of material distribution, in electronics for studying strontium oxide in vacuum tubes, activation of phosphors, source of ionizing radiation in luminous paint, cigarette density control, measuring silk density, atomic batteries, etc. 

In some gas-flow counter models, there is provision for placing a very thin window between the sample and the sensitive volume of the counter to reduce the effects of slight contamination of the sample well or of static charges that interfere with the measurement. In the counter of Fig. 5.24, the thin window will be placed on top of the sample well. A different arrangement is shown in Fig. 5.25. 

Eq.(l) shows that the full power of Stark spectroscopy is exploited only if the method is used with oriented samples. One obvious way to accomplish this aim is to incorporate the protein into LB structures. From a materials science view, this comprises the first step toward the design of a composite system, incorporating a functional entity into a lipid matrix. More important, this will facilitate an independent measurement of static and induced dipole moment changes. The directionality of the charge translocation can be determined in oriented samples, whereas, at present, it is only evaluated as a cone angle, 5, around the axis defined by the transition moment. 

Packed PTFE is not without its problems as a standard. The packed material is quite soft and is easily damaged by placing it with too much pressure against the reflectance port of the measurement instrument. In addition, the standards readily attract dust due to the formation of static charges on the powder induced during the packing process. Although not... 

Another electrification technique involves rolling a ball of test material for study in a cyhnder separated by an insulator. The two halves of the separated cylinder are then connected to an electrometer for measurement of the charge generated in the system. Peterson (1954) and Wagner (1954) have studied static electrification in this manner. Several observations may be made from these studies ... 

Surface Resistivity. Resistance is the measure of the conductivity of a material. Conductive materials have the abiUty to dissipate static charges. Therefore, resistance is a good measure of the abiUty of an object to dissipate a static charge. Since static electricity is primarily a surface phenomenon, the resistance along the surface of the object is of most interest. 

The static decay test is a good measure of the static dissipative nature of an object. However, the test is controlled by the object s resistance to ground. Objects that have a high resistance, such as insulators, will not readily accept an induced charge or decay an induced charge. The static decay test is most suited for objects with resistances of 10 or less (52). 

Static charge generation causes an ignition hazard only if the accumulated charges create an electric field sufficient to produce an electrical discharge in a flammable atmosphere. In most processes, this means that the electric field intensity at some location must reach the breakdown strength of air (nominally 3 X lO " V/m). The objective of static-control measures is to ensure that electric field intensities cannot reach this value. 

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