Research On All Solid State Low Noise Electric Field Sensor

As one of the most important underwater features,marine electric field signal is widely used in marine resources and seabed topography exploration,ship reconnaissance,submarine positioning and other fields.However,the seawater has the high conductivity,the marine electric field signals are mainly low frequency weak signals.Therefore,the noise level of the electric field sensor,especially the electrode as the core of the sensor,directly determines the accuracy of the measurement results.This thesis is aimed at the problem of low frequency and amplitude of marine electric field signal.A new type of solid state Ag/Ag Cl electrode is prepared by electrospray.The Ag Cl particles on the electrode surface are formed in the Polyvinylpyrrolidone（PVP）system.PVP is a kind of nonionic polymer compound,which can not only be used to form the precursor solution of electrospray,but also control the reaction speed and the shape of the product,so that the size of Ag Cl is small and the shape is regular.First,under high voltage,the polymer solution is atomized onto a clean silver rod cleaned with hydrochloric acid.Then,PVP is removed by high temperature calcination to reduce electrode impedance and form the porous surface.Finally,a porous electrode shell with a protective layer of silica is designed to reduce the noise caused by seawater flow,slow down the decomposition of Ag Cl and increase the electrode life.The preparation method increases the specific area of the electrode reaction layer,shorts the time to establish the reaction equilibrium,and reduces the number of abnormal reaction elements,so that the electrode has the characteristics of high stability and low noise as an ocean electric field sensor.The performance of the sensor is analyzed by microscopic characterization and electrochemical testing.The results of scanning electron microscopy（SEM）show that the Ag Cl particle size ranged from 1.2 μm to 1.7μm,with an average particle size of 1.43μm.The impedance,active electric field response,self-noise and stability of the electrode are measured to study the electrochemical performance of the electrode.The impedance of the electrode is 7.9Ω and shows resistance characteristics,meaning that the electrode can well receive the weak ocean electric field signals with low signal distortion.The sensitivity experiment result shows that the electrode can well restore the sinusoidal electric field signal of 1Hz（10m V）.The voltage drift is less than 5μV/100 h,the self-potential is between-51μV to 56μV and self-noise of the electrode is 2.48 n V/√Hz @1Hz.Finally,a chopper amplifier is designed to eliminate the 1/ f noise of the marine electric field signal,and the effectiveness of the electrode is further verified by laboratory underwater experiments.All the experimental results show that the electrode has ultra-low noise and excellent response to low frequency weak electric field signals.The electrode is of great significance to the exploitation of marine resources as the marine electric field sensor.