A Noninvasive Resonant Galvanometer With Multiple Measurement Ranges

Noninvasive, real-time monitoring of large-span currents in power grid and electric vehicles remains a challenge. A resonant galvanometer (RGM) achieving multiple measurement ranges with a single sensing unit is proposed in this article. An electromagnetic torque introduced theory for ac measurement is established to analyze the deviated output voltages, which have not been well physically interpreted and theoretically characterized so far. The deviated output voltages are defined as two asymmetric subpeaks for the first time. According to the Euler–Bernoulli beam theory, two asymmetric subpeaks have the potential to achieve multirange measurement with the main peak, which is at the magnetic field gradient extremum and directly opposite to the cable. A multirange sensing mechanism is proposed with three peaks, comprised of two newly defined asymmetric subpeaks and one main peak. Measurement ranges of the two subpeaks are two and five times than that of the main peak, respectively. Geometrical design of the sensing unit is analyzed to further adjust the multiranges via three peak values. A prototype with a single sensing unit is designed and fabricated to achieve multiple measurement ranges, and its practical applications in power grid and electric vehicles are also considered.