公开(公告)号：JPS6255548A

公开(公告)日：1987-03-11

申请号：JP19478985

申请日：1985-09-05

Applicant: ALOKA CO LTD

Inventor： TOKUTAKE MASAAKI ,  OTA KIYONORI ,  YANAI TOSHIO ,  SATO WATARU

IPC: G01N23/06 ,  G01N15/06

Abstract: PURPOSE:To enable the checking for the abnormality of sensitivity at a detector section, by arranging a detector section driving part to stop a detector section at a position away from a filter paper between blank and major measuring positions to allow the measurement of air alone free from a filter paper. CONSTITUTION:A rollable filter paper 14 is introduced 16 into a trapping section 10 to trap 14 floating dust contained in air passing through the trapping section 10 and the filter paper 14 is sent to a measuring position with a winding reel 18. A detector section 24 comprising a beta ray source 20 and a beta ray measuring device 22 is so arranged to be stoppable at a sensitivity checking position C away from a filter paper 1 while it moves from a blank measuring position B (measurement before dust collection) to a major measuring position M (measurement after dust collection). Then, a blank measured value is inputted into a memory 34 through a controller 32 while a sensitivity check measured value is inputted into a memory 36. Then, after the end of a sensitivity checking measurement, transmission B dose through the filter paper 14 collecting dust is measured 24 and inputted into a density computing unit 42 which calculates the ratio with the blank measured value and computes the density of a floating matter to record 40.