Development and application of a compact ocean bottom electromagnetometer based on ARM embedded system

Ocean bottom electromagnetometer (OBEM) is used for picking and recording electromagnetic signals on seafloor. However, most of them are large, heavy, costly and low operational efficiency. Therefore, to improve these problems, we have developed a compact ocean bottom electromagnetometer. In order to reduce cost and deck space, we integrated acquisition system, acoustic transducer, fluxgate sensor and batteries into a 17-inch glass sphere; assembled other components including anchor, electrodes and electric dipole arms outside. An ARM Cortex-M microcontroller is used as the control unit. By combining with other low power design, the total power consumption is only 400mW at 250Hz sampling frequency, the lithium batteries can supply OBEM running for more than 3 months. In order to evaluate the reliability of OBEM, a number of ocean experiments were carried out in South China Sea, Mariana Trench and Antarctic Peninsula. All instruments were recovered successfully and high quality magnetotelluric data was obtained.