Flexible Ruhmkorff coil, primarily used for measuring and protecting high currents. The coil outputs a voltage signal, which is the derivative of the current value over time, thus requiring an integrator to restore the phase of the measured current. The Ruhmkorff coil boasts excellent transient response capabilities, with no hysteresis or magnetic saturation, a wide measurement range, high precision, and a broad frequency response range. The coil requires minimal installation space, is lightweight, and is easy to install without damaging the conductor. It is widely used in measurement environments where traditional current-measuring CTs are not convenient.