| 摘要 |
PURPOSE:To obtain a protecting device for a photodetector element of an optical measuring apparatus, in which the element designed to receive light of very low intensity is shielded from strong external light. CONSTITUTION:While a photomultiplier is held in a light-blocking case 5, openings 5a and 6a making the light-blocking case 5 and a cover part 6 communicate with each other are provided and a knurled screw 31 the fore end part of which comes into contact with a limit switch 33 is provided through the openings 5a and 6a. When loosening of the knurled screw 31 is started for opening the cover part 6, the limit switch 33 is put in an open state at once, an impression voltage of the photomultiplier is put in an OFF state and thus the photomultiplier can be protected.
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