The current noise indices (C.N.I.) depend linearly on the logarithmic values of sheet resistivity(log ρS), in both carbon black/resin and thallium oxide/glass resistors, and can be expressed asC.N.I. = A + B log ρS. The geometrical dependency on C.N.I. in both types of resistor can be expressed asC.N.I. = A′ − B′ log (L, W, T), whereA,B,A′ andB′ are constants. The dependency of noise e.m.f. (νn) on the applied dc voltage (V), i.e., the values ofαinνn2¯∝Vα, can be obtained from the slope of C.N.I. versuslog (L)lines, associated with a model based on the noise generator approximation.
The Kelvin generator is an amazing electrostatic device which poses many questions. Here we report the results of our investigations of this device under various controlled conditions with both non-polar and polar liquids and a sodium chloride aqueous solution. Further we have found that the generator works well even if the two liquid streams originate from different electrically insulated reservoirs. In addition we propose a model in which the electric charge results from the separation of the hydrogen and hydroxyl ions as the water droplets form.
The percentage variation of resistance of polymer thick film (PTF) resistors has been studied. Two different kinds of polymer resin, i.e., epoxy resin and polyimide resin, as well as four different kinds of carbon black are adopted in the preparations of PTF resistors. Among the four different kinds of carbon black, i.e., e45, MA-100, MA-600 and HS-500 (all trade names), HS-500 shows the least variation with temperature changes. This can be attributed to the high structure property of HS-500 carbon black. The variation will be lowered down with an increase in the loading fraction of carbon black in PTF resistors. Same tendency will be observed in both epoxy and polyimide resin PTF resistors. However, the variations are smaller in polyimide resin resistors than in epoxy resin resistors. The percentage variations of resistance of PTF resistors, after stored at 120C for 1000 hrs, or after 25 cycle thermal shock tests, or dipped in a 200C solder pot for three seconds, as well as the variations after the short term overload tests, have also been measured and studied. The variations are still smaller in polyimide resin PTF resistors. A possible explanation on this smaller variation in polyimide resin PTF resistor is also presented.
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