Multi-node wireless drifting buoy for shaft-rate electric field measurements

Underwater electric field measurement is critical for ship localization in subsea engineering and coastal defense monitoring. Acoustic, optical, and magnetic sensing technologies have each been successfully used for underwater positioning and detection; however, their performance can be affected by environmental factors, including multipath propagation and attenuation for acoustic links, water turbidity and illumination for optical methods, and geomagnetic or platform magnetic interference for magnetic sensors. Shaft-rate electric-field sensing is, therefore, treated here as a complementary signature channel rather than a replacement for mature acoustic methods. Existing electric-field measurement platforms, including seafloor observatories and towed arrays, still face limitations such as environmental-noise sensitivity, deployment cost, and recovery risk. To address these challenges, this study proposes a multi-node wireless drifting electric-field buoy system. It integrates triaxial differential electric-field sensors, low-noise acquisition circuits (<6.8 nV/Hz at 1 Hz), and low-voltage differential signaling transmission, achieving a dynamic range of 118 dB over a DC-20 Hz bandwidth for weak electric-field measurement. GPS PPS timing provides a common timing reference for distributed nodes, while LoRa wireless communication and real-time processing support efficient data transmission. Pool experiments with one complete receiver set successfully captured simulated 5 Hz shaft-rate E-field signals. Short-time Fourier transform analysis showed clear fundamental and harmonic components with high signal-to-noise ratios. The results validate the single-receiver measurement capability and provide a basis for future field tests and multi-buoy synchronization validation in complex aquatic environments.