JPS6475968A - Measuring device of current - Google Patents

Abstract

PURPOSE:To improve the accuracy in measurement by providing two gap parts in a single core with a gap and by providing magnetic field sensors different in sensitivity in the gap parts respectively. CONSTITUTION:A core 2 with a gap having gap parts 3 (3a, 3b) is provided around a conductor 1, and magnetic field sensors 4 (4a, 4b) being different in sensitivity are inserted into the gap parts 3 respectively, while the sensors 4 are connected to a measuring element 6 through optical fibers 5 (5a, 5b) respectively. A magnetic field generated by a current flowing through the conductor 1 forms a magnetic circuit in the core 2. In the gap parts 3 magnetic fields proportional to the current flowing through the conductor 1 are generated and impressed on the sensors 4. The gap lengths of the gap parts 3 are equal, and therefore the magnetic fields impressed on the sensors 4 are also equal. A light sent from the measuring element 6 to the sensors 4 through the optical fibers 5 is subjected to light intensity modulation in accordance with the magnetic fields impressed on the sensors 4 and sent to the measuring element 6 through the optical fibers 5. In the measuring element 6, either one of two electric signals, which is found within a current measuring range, is selected by a selecting means and outputted.