Multi-dimensional Electric- and Magnetic-field Sensor for Low-frequency Applications

A growing number of electric-field sensors and magnetic-field sensors are becoming commercially and federally available. However, there is a lack of compact sensor systems that integrate both modalities for more advanced sensing scenarios. The CCDC Army Research Laboratory has developed a "4-D Cube" sensor which precisely measures the local 3-D magnetic field and 1-D electric field at frequencies between 30 Hz and 32 kHz. By using a non-metallic transducer for the electric-field sensor, and three loop sensors without a ferrite core for the magnetic-field sensors, we minimize cross -axis and cross modality field distortion, even when these sensors are placed in close proximity to each other in an array. This paper will cover the quasi-static field theory behind the design of the complete sensor system, and characterization results of the electric- and magnetic-field sensors for frequency response and noise spectral density. The 4 -channel analog sensor is approximately 200 x 200 130 mm, weighs under 0.5 kg, and consumes less than 50 mW during full operation. Cross-axis effects have been measured to be <= 5%. The noise spectra is <10 mA/m and <1 mV/m over most of the 32 -kHz frequency range, and all sensors have >80-dB dynamic range regarding single-tone signals.