Rocoil 4000 Series
The Rocoil® Type 4000 flexible Rogowski coils are available in a range of lengths up to several metres in screened and un-screened versions. Type 4000 coils differ from the Type 1000 series coils in that the ends of the coil are aligned by overlapping them which results in a simplified construction. Most Type 4000 coils are built with a small cross-sectional diameter of about 6mm which gives very good flexibility.
4000 Series Features
With a suitable electronic integrator these coils can be used to measure low currents with a resolution as low as 10mA and high currents of greater than 1MA. The Rogowski coil sensors provide complete isolation from the circuit being measured and have no effect on the current being measured even for very low-impedance circuits.
There are other devices that measure electric current without making electrical contact with the conductor. Many of these, including the conventional current transformer, use a ferromagnetic core and are subject to magnetic saturation effects that limit the range of currents that they can measure.
- A Rogowski coil, on the other hand, is ‘linear’; it does not saturate and the mutual inductance between the coil and the conductor is independent of the current. Many of the useful features of Rogowski coil systems result from their linearity.
- They have a wide dynamic range so that the same coil can be used to measure both very small and very large currents. Calibration is easier because the coil may be calibrated at any convenient current level and the calibration will be accurate for all currents including very large ones.
- Coils can be built which are very compact and can be fitted in confined spaces. They are thus very useful for retro-fit applications.
Flexible Rogowski coils can be used for measuring electric current in large or awkwardly-shaped conductors, where space round the conductor is limited and for the measurement of very large currents (thousands of kA).