| 摘要 |
PURPOSE:To improve the measuring accuracy of dust density, by measuring the pressure in an irradiation path or a discharge path, and compensating a measuring error by the pressure caused by clogging of a filter medium, etc. by settling of dust, by use of said pressure measured value. CONSTITUTION:Intensity of beta-rays reaching a detector 17 is measured, and this measured value I0 is stored temporarily in a control operating part 3. Thereafter, a suction pump 12 is operated, by which collection of air is started. Dust is filtered by a filter medium 1a, a settling layer 21 is formed, its thickness increases as time passes, and intensity of beta-rays reaching the detector 17 continues to decrease gradually, but a measured value I is always sent to an input/output port of the control operating part 3. Pressure and temperature in a flow path 6 of the downstream side from the filter medium 1a are measured by a detecting end 13 and a temperature sensor 14, and by use of these measured values, a measuring error caused by variations of pressure, temperature and flow rate contained in the value of I0 at each measuring time is compensated by the control operating part 3, and dust density C is calculated, and is displayed continuously on a display part 20. |
