Voltage step method

The voltage-step method is, however, analogous to the TOF method and has been used in studies of semiconductive polymers. The theoretical transient current response is similar to that shown in the upper curve in Fig. 8.30(b). It rises from its initial value to a maximum and then falls away to a steady state... 

The simplest transient method for the study of rapid electrode processes is the voltage step method. It consists of applying a sudden voltage step to an electrochemical cell initially at equilibrium. This voltage step is applied across the cathode and anode and the current passing through the cell is... 

Fig. 68. Potential and current-time curves of the voltage step method.

Equation 5.29 predicts that for = 0, as is the case with the potential step method, one does not have to worry about the capacity current. Therefore the time of measurement can be as short as practicable, contrasting with the case of the voltage step method. Using the same criterion of the maximum j o that can be conveniently measured as for the voltage step method, we get for the slope... 

Exposure of a human body to touch and step voltages and methods to deal with these are also covered. Grounding and ground fault protection schemes are described in detail with illustrations to help an engineer to select the most appropriate grounding method and ground fault protection scheme for a machine or system. 

Such effects are observed inter alia when a metal is electrochemically deposited on a foreign substrate (e.g. Pb on graphite), a process which requires an additional nucleation overpotential. Thus, in cyclic voltammetry metal is deposited during the reverse scan on an identical metallic surface at thermodynamically favourable potentials, i.e. at positive values relative to the nucleation overpotential. This generates the typical trace-crossing in the current-voltage curve. Hence, Pletcher et al. also view the trace-crossing as proof of the start of the nucleation process of the polymer film, especially as it appears only in experiments with freshly polished electrodes. But this is about as far as we can go with cyclic voltammetry alone. It must be complemented by other techniques the potential step methods and optical spectroscopy have proved suitable. 

Simulators today sport many DC convergence options that are generally invoked automatically when the basic method fails. These include GMIN stepping, source stepping, initial capacitor voltage stepping, and... 

Potential step method Chronoamperometry Chronocoulometry Voltage pulse method Pulse polarography Differential pulse polarography... 

As of this writing (ca 1993) there are eight methods of erythrocyte entrapment. Six methods depend on loading via hypotonic exchange, one method dc icnds on chlurpromazine-induced endocytosis. and one depends on voltage-step induced transitory permeation,... 

Conduct a series of tests using the stair step method. When there is an ignition, decrease the voltage one step for the next test. When there is no ignition, increase the voltage one step for the next test. 

The measurement of dielectric strength (Figure 3.52a) is usually carried out either by the short-time method or by the step-by-step method. In the former method the voltage is increased continuously at a uniform rate (500 V/sec) until failure occurs. Typically, a 1/8-in. thick specimen requiring a voltage of about 50,000 V for dielectric failure will thus involve a testing period of 100 sec or so. 

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