An ultralow-noise Ag/AgCl electric field sensor with good stability for marine EM applications

This paper presents an ultralow-noise level of Ag/AgCl electric field sensor for detecting seafloor electric field signals. During the anodization process, we used a constant current and a constant potential for achieving the ultralow-noise level and for improving the stability and repeatability of the Ag/AgCl electric field sensor, respectively. We took advantage of newly developed materials to generate high-quality Ag/AgCl electric field sensors. Typical measured noise level is 0.6 nV/rt(Hz) at 1 Hz. The source resistance between pairs of Ag/AgCl electric field sensors is approximately 5 Ω, almost independent of frequency between 0.1 Hz and 10 Hz. The offset potential is typically below 0.1 mV with a drift of less than 5 μV/day and less than 10 μV/°C. This Ag/AgCl electric field sensor has promise for improving the accuracy of marine electric field measurements.