Motion Noise of an Electrode Sensor and Its Relationship with Fluid Velocity Fluctuations
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ISTICAL RADIOPHYSICS
Motion Noise of an Electrode Sensor and Its Relationship with Fluid Velocity Fluctuations V. G. Maksimenko* Fryazino Branch, Institute of Radioengineering and Electronics, Russian Academy of Sciences, Fryazino Moscow oblast, 141190 Russia *e-mail: [email protected] Received March 15, 2019; revised March 15, 2019; accepted October 30, 2019
Abstract—The theory of the occurrence of voltage ripples at an electrode sensor as it moves relative to an electrolyte (in particular, seawater) has been refined and supplemented, which takes into account two different mechanisms for the occurrence of ripples. Formulas are obtained that relate the jump in the electrode potential to the jump in the flow velocity, which are applicable to real-size electrodes during prolonged exposure in an electrolyte. It is shown that the calculated ripple voltage coincides in order of magnitude with that obtained in experiment. DOI: 10.1134/S1064226920090065
INTRODUCTION Electric field electrode sensors in an electrolyte, in particular, in fresh water and seawater, are widely used, e.g., in measuring artificial and natural electric fields in the ocean, electromagnetic communication systems with an underwater object, in electromagnetic flow meters [1–3]. In our experimental studies, a relationship was found between the noise of an electrode sensor moving with respect to a fluid (motion noise) and motion velocity fluctuations [4, 5]. The intrinsic noise of the sensor limits its sensitivity, so studying its causes is a relevant issue. Study [6] considers the mechanism of the change in the potential (polarization) of an electrode in a flow. It is based on incidentflow deformation of a double electric layer (DEL) at the leading edge of the electrode. Expressions are obtained for the magnitude of the excess charge on the electrode and the change in potential. However, the developed theory is applicable only to very small electrodes. In [7], another mechanism was considered for the change in the electrode potential in an electrolyte, based on the change in the rate of oxygen adsorption by the electrode surface due to the modulated thickness of the diffusion layer. The obtained formula for changing the potential is in good agreement with the results of experimental studies with the exposure time of the electrode in the electrolyte for several hours. However, the measured electrode noise during prolonged exposure of the electrodes in the electrolyte significantly exceeds the theoretical values. The purpose of the article is to clarify the developed theory of the occurrence of motion noise for
electrodes of real size and with prolonged exposure of the electrodes in the electrolyte. 1. PULSATION OF ELECTRODE CAPACITANCE DURING DEFORMATION OF THE DEL (POLARIZATION NOISE) When the electrode is immersed in the electrolyte, a double electric layer is formed on its surface, similar to a lossy capacitor. For metals commonly used in electrodes with a dense oxide dielectric film on their surface (Ta2O5TiO2), the formation of a double layer
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