Heated wire electrodes, temperature determination

Sigmoidal voltammograms at permanently heated wire electrodes proved very useful for analytical application since their limiting current can be determined easily. The latter is strictly proportional over some orders of magnitude to bulk concentration of the electrolysed species in solution. An extra benefit is the increased temperature which improves kinetic behaviour. Since temperature is increased only close to the microelectrode, constituents of bulk volume keep unaffected. This proved useful for analysis of dissolved gases and sensitive substances. 

The hot-wire anemometer, principally used in gas flow measurement, consists of an electrically heated, fine platinum wire which is immersed into the flow. As the fluid velocity increases, the rate of heat flow from the heated wire to the flow stream increases. Thus, a cooling effect on the wire electrode occurs, causing its electrical resistance to change. In a constant-current anemometer, the fluid velocity is determined from a measurement of the resulting change in wire resistance. In a constant-resistance anemometer, fluid velocity is determined from the current needed to maintain a constant wire temperature and, thus, the resistance constant. 

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