Magneto:optical current measurement transducer - uses polarisation plane rotation to avoid shape birefringence from angled photoconductor coil

摘要

A magneto-optical current converter for measurement of currents uses a photo-conductive coil of fibres surrounding a current conductor carrying the current to be measured. It is developed to compensate for shape double refraction or birefringence. The device is constructed without inbuilt mechanical stress as in 2445369 to eliminate stress birefringence. A linear polarised light ray is passed through the fibre coil and its polarisation plane is rotated by the magnetic field of the current in the conductor (10) to give a measure of the current. The degree of rotation may be affected by birefringence due to the coil shape. The coil is constructed with a helix angle greater than thirty degrees.