What is a Rogowski coil?

A Rogowski coil, also known as a Rogowski coil or an open-core coil, is a flexible sensor with a clamping design. It can be easily wrapped around a current-carrying conductor to measure currents of several thousand amperes without significantly increasing the size of the transformer. As an electronic current transformer, the Rogowski coil is suitable for detecting alternating currents, including high-speed transients, pulse currents of power devices, and 50 Hz or 60 Hz sinusoidal currents in industrial frequency.

The Rogowski coil is extremely thin and flexible, which makes it precise and prone to damage during use. Therefore, it requires careful handling to ensure long-term stable operation.

If you need to measure flexible alternating currents in the tens of amperes range, a Rogowski coil current probe is a worthy choice.

The measurement principle of the Rogowski coil

Its operation is based on Faraday's law of electromagnetic induction, which states that the induced electromotive force in a closed loop is proportional to the rate of change of the magnetic flux through the loop.

Similar to traditional AC current transformers, the Rogowski coil measures by generating a voltage signal in the secondary coil that is proportional to the current in the main insulated conductor. The main difference lies in the magnetic core structure: the Rogowski coil uses an open-core design, while conventional current transformers use a high-permeability iron core with a secondary winding to achieve magnetic coupling. The open-core structure helps reduce insertion impedance, resulting in faster signal response and higher voltage linearity.

The coil is arranged in a ring around the current-carrying conductor. When alternating current flows through the conductor, the changing magnetic field around it induces a voltage in the coil. The output voltage of the Rogowski coil is proportional to the rate of change of the current over time (i.e., the derivative of the current). Subsequently, an integrating circuit processes this voltage, ultimately outputting a voltage that is proportional to the input current signal from the probe.

The ETA Rogowski coil flexible current probe can measure up to 6000 A peak AC current at most.