| 摘要 |
PURPOSE:To make it possible to detect the effect of the flow rate of attachment preventing air on transmitting light by additionally providing flow-rate regulating valves in paths of powder-attachment preventing air. CONSTITUTION:Light from a light source 3 which is provided in the side wall of a powder feeding pipe 1 crosses a stream 2 of powder and reaches a photodetector 4. After optoelectronic transducing action, the signal is guided into a signal processor 6. Air pipes are provided at the provided part of the light source and the provided part of the photodetector for preventing the attachment of the powder. Powder-attachment preventing air streams 12 and 13 are introduced. Flow-rate regulating valves 7 and 8 are provided at the intermediate parts of the air pipes. The flow rates of the attachment preventing air streams 12 and 13 are periodically changed based on average flow rates, widths of flow-rate changes, period signals of flow rate change and the like with a flow rate controller 9. Said average flow rates, widths of flow rate changes, period signals of flow rate change and the like are inputted into the signal processor 6 from the flow rate controller 9. The signal processor 6 performs the differential operation of the intensity of the transmitted light based on the input signal. The lowest intensity of the transmitted light when a pulse is generated is operated. Thereafter, the intensity of the transmitted light is periodically sent out 11. In this way, the effect of the flow rate of the attachment preventing air on the transmitted light can be detected. |
