Abstract: A current measuring apparatus comprises a current detection unit 10 and a photoelectric converter 20. The current detection unit 10 comprises an optical fiber sensor 11 extended or looped around a conductor 30. A reflective film 12 is attached to one end of the sensor 11 so that light can be reflected by the end of the sensor. The current detection unit 10 further comprises a first Faraday element 13, a light-transmitting birefringent member 14, a first optical fiber 15, a second optical fiber 16 and a lens 17. The Faraday element 13 rotates a plane of polarization of the incident light through about 22.5°. The birefringent member 14 functions to separate the light emitted from the sensor 11 into an ordinary ray L1 and an extraordinary ray L2 that are orthogonal to each other, and to transmit linearly polarized light L0 emitted from a light source. The lens 17 is provided between the element 13 and the birefringent member 14.

Abstract: A current measuring apparatus comprises a current detection unit 10 and a photoelectric converter 20. The current detection unit 10 comprises an optical fiber sensor 11 extended or looped around a conductor 30. A reflective film 12 is attached to one end of the sensor 11 so that light can be reflected by the end of the sensor. The current detection unit 10 further comprises a first Faraday element 13, a light-transmitting birefringent member 14, a first optical fiber 15, a second optical fiber 16 and a lens 17. The Faraday element 13 rotates a plane of polarization of the incident light through about 22.5°. The birefringent member 14 functions to separate the light emitted from the sensor 11 into an ordinary ray L1 and an extraordinary ray L2 that are orthogonal to each other, and to transmit linearly polarized light L0 emitted from a light source. The lens 17 is provided between the element 13 and the birefringent member 14.

Abstract: A compact and inexpensive refractory monitoring temperature sensor and a compact and inexpensive refractory erosion location measuring device which can effect continuous detection of erosion over a wide range and specification of a location of an erosion and further can be re-used and used continuously. The temperature sensor includes at least two metal members and an insulating substance (2) filled between the metal members. The sensor detects a condition of an erosion of a refractory not from a melting breakdown of the sensor but from a variation in insulation resistance of the insulating substance which arises from a high temperature of the refractory due to erosion of the refractory. The measuring device incorporates such temperature sensor and discriminates an amount and a location of erosion of the refractory from a variation in insulation resistance between the metal members.