Analysis and suppression of Joule heating errors in NV-center high current measurement within enclosed power equipment

Current measurements are crucial for monitoring power systems, diagnosing faults, and metering energy. The growth of ultra-high-voltage transmission, smart grids, and renewable energy integration has increased the demand for high-precision current sensors. Diamond nitrogen-vacancy (NV) centers present a promising platform for these applications because of their high magnetic sensitivity. Nevertheless, most existing studies emphasize performance optimization in open environments with sufficient heat dissipation, largely neglecting the thermal interference caused by Joule heating in enclosed power equipment. This study established a coupled thermal field model to elucidate the temperature distribution and complete error transfer chain from Joule heating to NV energy level shifts, leading to equivalent current errors. To mitigate this thermal error, a dual-channel microwave differential frequency locking method was employed to decouple temperature-induced drifts from the magnetic field signals. The system achieved a sensitivity of 27 mV/A and a measurement error of 0.06%, with an RMS noise of 0.56 mA Hz−1/2 and an Allan deviation stability of 0.4 mA. Significantly, the dual-channel approach reduced the measurement error from 0.83% (single-channel) to 0.06%, demonstrating an order of magnitude improvement under a sustained thermal offset. These findings provide a practical solution for high precision online current monitoring in enclosed power equipment, where Joule heating has long posed a significant challenge to the measurement accuracy.