| 摘要 |
1,207,540. Photo-electric current measurement. COMPAGNIE DES COMPTEURS Nov. 16, 1967 [Nov. 25, 1966; Feb.7, 1967], No.52276/67. Headings G1A and G1U. In a system for measuring the current in a high voltage transmission line, where the current, or a current proportional to it, rotates the plane of polarization of a light beam by the Faraday effect, two polarized beams are rotated by the current in opposite directions and received via analysers upon respective photo-cells connected in a differential arrangement. The present system avoids interference from outside magnetic fields and variations in the light source or sources producing the beams. In a null-arrangement Fig. 1 two beams polarized by polarizers 11 and 21 are rotated in opposite directions by first optical elements 12, 22 whose windings are energized by a current proportional to the one being measured. The beams are rotated back by optical elements 13, 23 whose windings are traversed by current proportional to the difference in the two photoelectric voltages generated by photo-cells 15 and 25 on which the two beams finally arrive after passing through analysers 14 and 24. The current through the windings of elements 13 and 27 is proportional to the current being measured and is indicated at 9. In another arrangement Fig. 3 (not shown) the light beams of equal intensity are generated by diodes and intensity modulated at a frequency proportional to the level of current being measured. This frequency modulation appearing in the differential detector circuit is detected as an additional measurement of the current. In another arrangement Fig. 2 (not shown) optical elements 12 and 22 have no windings but are placed either side of the conductor through which the current being measured flows so that the elements are influenced by the magnetic field of the conductor. |
