DETECTOR FOR OIL OR THE LIKE

摘要

PURPOSE:To detect oil or the like accurately by making outside mediums discharge the duties as a clad and providing an optical fiber or the like to make its core contact with these outside mediums. CONSTITUTION:The core 3 of a detection part 2 of the optical fiber 1 is constituted nakedly without the clad 4. In case the oil or the like is detected by an optical fiber detection sensor 5 constituted by using the fiber 1, the quantity of photofdetection in a photodetecting element 8 increases and decreased gradually with the lapse of a long period in a detectio circuit. Such a change of the quantity of photodetection can be compensated by a signal change compensating means in an arithmetic and control circuit 10 and accordingly, a photodetected signal inputted to a change rate comparing means 19 can be maintained almost constantly usually. Accordingly, when the oil is stuck on the naked core 3 in the detection part 2 of the fiber 1 in the state, the photodetection output is lowered in a short time and the detection output of the oil or the like is obtained by comparing it with a set signal 17 with the means 19 and a command 18 can be given to an alarm circuit 11.