| 摘要 |
PURPOSE:To improve detecting accuracy by controlling the flow rate of specimen air so that the flow rate becomes a preset flow rate based on the detected temperature from a temperature sensor and the free air temperature from a free air temperature sensor. CONSTITUTION:Light which is outputted from a light source 19 is concentrated at a detecting part 6. Convection occurs in air which is heated with heaters 11 and 12. Specimen air flows through the part 6. The scattered light from particulates in the specimen air is received with a photodetector 23 through a condenser lens 25. Then, an output signal from the photodetector 23 is inputted into a central processing unit 30 through an amplifier 28 and a waveform shaping device 29. The number of the particulates is counted, and specified operation is performed. The detected temperature of a temperature sensor 17 and the preset value of a first preset device 35 are compared in a first comparator 34. The free air temperature of a free air temperature sensor 36 and a standard temperature of a second preset device 37 are compared in a second comparator 38. The deviation signal of the comparators 34 and 38 is corrected in an operation amplifier 39. A current controller 40 is driven. Thus the specimen air having the preset flow rate can be always made to flow. |
