Vibrating plate/condenser method

A dynamic method for the measurement of dynamic surface potentials in the range 0.005 to 1 seconds has been described by Kretzschmar (1965). This device consist of a rotating rod dipping into the surfactant solution. The rotating rod transports a film of the surfactant solution below a vibrating plate condenser to determine the surface potential. As the age of the liquid surface is a direct fimction of the rotational speed, the time dependence of the surface potential is obtained. Fig. 1.8. demonstrates of this principle. 

In the dynamic condenser, or the vibrating plate or vibrating condenser method (Fig. 5), also called Kelvin, Zisman, or Kelvin-Zisman probe, the capacity of the condenser created by the investigated surface and the plate (vib. plate) is continuously modulated by periodical vibration (GEN.) of the plate. The ac output is then amplified and fed back to the condenser to obtain null-balance operation (E,V). " " ... 

In contrast to the ionizing electrode method, the dynamic condenser method is based on a well-understood theory and fulfills the condition of thermodynamic equilibrium. Its practical precision is limited by noise, stray capacitances, and variation of surface potential of the air-electrode surface, i.e., the vibrating plate. At present, the precision of the dynamic condenser method may be limited severely by the nature of the surfaces of the electrode and investigated system. In common use are adsorption-... 

The two metals act as the plates of a condenser, one of the plates being used for adsorption of the gas and the other being a reference electrode. Adsorption of gas causes a change in contact potential equal to the change in work function. Disappearance of the electrical field between the two plates may be detected either by the steady condenser method or the vibrating condenser method ... 

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