| 摘要 |
PURPOSE:To always maintain accurate detection operation without receiving the effect of dust, by providing shield plates each having a small hole in two receivers and passing only the light passing the central parts of the opening parts provided to the peripheral walls of said receivers among lights from a light emitter to a light receiver. CONSTITUTION:Receivers 30, 40 opened through peripheral wall opening parts 22a, 22b are arranged to both sides of an introducing body 20 introducing a fluid to be detected in opposed relationship. A light emitter 50 emitting light toward the opening part 22a is provided to the receiver 30 and a light receiver 60 receiving light from the light emitter 50 through the opening part 22b is provided to the receiver 40. Shield plates 32, 42 having opening parts 32a, 42a are respectively provided in the receivers 30, 40 and the light from the light emitter 50 is passed only through the central part of the opening part 22a and only light passing through the central part of the opening part 22b in the light from the opening part 22a is received by the light receiver 60. By this method, the light emitter and the light receiver are certainly blocked from dust to be protected from contamination and light receiving quantity is not reduced even if dust is adhered to the inner periphery of the each opening part, and accurate detection operation can be secured. |
