SOAP FILM TYPE FLOWMETER

PURPOSE:To stick and form a thin soap film uniformly and to measure accurately a gas flow rate by slanting the end surface of the lower opening of a volume tube, drooping the lowermost end further downward and forming a liquid drip part, and providing a film receiving ring which has a necessary diameter at the periphery of the lower opening. CONSTITUTION:A soap film is formed on a film forming ring 7 halfway during a return by a solenoid 5 to a home position from in soap liquid and then sticks on the film receiving ring 15 which diameter becomes larger than the lower opening 4A forming the slanting surface of the volume tube 4 and smaller than the ring 7, thereby forming the specific soap film 13 on the film receiving ring 15. This film 13 cuts off a flow of measurement gas G flowing in the volume tube 4, so the film sticks on the lower opening end surface 4a of the tube 4 with the gas pressure to seal the entrance of the tube 4. At this time, excessive soap liquid which does not contribute to the formation of the soap film falls speedily along the lower end surface 4a and liquid dip part 14, so no liquid stays on the end surface 4a. Then the soap film which sticks on the end surface 4a rises in the volume tube 4 with the gas pressure and passes a start detector 11 and a stop detector 12, and the time T required for the passage between both the detectors is measured to find the flow rate of the measurement gas G from the time T and a capacity value V. This constitution can stick and form the desired thin soap film on the lower opening of the volume tube without giving any influence upon the diameter of the volume tube and the gas flow rate can accurately be measured.