THE INFLUENCE OF THE NEAR-ELECTRODE IMPEDANCE OF THE CAPACITIVE SENSOR ON THE RESULT OF MEASURING THE ACTIVE AND REACTIVE COMPONENTS OF THE IMMITANCE

Influence of near-electrode impedance of capacitive sensor on result of measuring the active and reactive components of the admittance of electrolytic objects is considered. Near-electrode impedance is formed by capacity of the double layer and the Warburg impedance. Reactive and active components of admittance are the informative parameters of object’s electro physical parameters, in particular dielectric permittivity and specific conductivity. Product quality is assessed by comparing the reactive and active object components of the impedance or admittance with the corresponding parameters of the standard samples. Significant influence on the result of measuring immittance components of such objects is fixed at low frequencies. However, we need to measure the electro physical quantities at the mentioned frequencies.

So we develop the mathematical models of reactive and active components at different frequencies and analyse the obtained results for evaluating the effect of near-electrode impedance. Dissimilar impact of the near-electrode impedance parameters on its active and reactive components is revealed. It is shown that at low frequencies the reactive component of the near-electrode impedance depends on the double layer capacity and does not depend on the parameters of the Warburg impedance.

At higher frequencies, the active component depends on similar resistance as well as on the tangent of the parallel connection angle of the double-layer capacity and polarization resistance. Corresponding equivalent circuits of the contact capacitive sensor with the measured object are given.

Regarding the research of mathematical models of active and reactive components of immittance control objects of non-electric nature, in particular electrolytic substances the conclusions are fulfilled. In order to reduce the methodological error it is not recommended to apply the substitution scheme of the contact capacitance sensor, since the impact of the parameters of electrode impedance differs for inadequate measuring modes. Therefore, for analysis of mathematical models of immittance active and reactive components of measuring object, the appropriate substitution scheme is recommended.