| 摘要 |
<p>PROBLEM TO BE SOLVED: To realize a gas flowmeter which is small, whose structure is simple and whose rangeability is wide in such a way that the hunting of a flapper valve is suppressed so as to eliminate the pulsation of a flow passage, that the durability of the flapper valve is increased and that the operation of the flapper valve is stabilized. SOLUTION: When a flow rate is at a set small flow rate or less, the flapper valve 18 comes into contact with a frame-shaped edge part 30. A gas flows into a bypass flow passage 17A from an entrance port 17a, and it flows to the downstream side of the flapper valve 18 in a main flow passage 16 from an exit port 17b. The small flow rate at this time is measured by a thermal flow sensor (not indicated in the figure) in the bypass flow passage 17A. When the flow rate is increased the flapper valve 18 is opened up to an angle B, The flapper valve 18 is situated on the downstream side of the exit port 17b, and the total flow rate is measured by an estimation-type gas flowmeter (not indicated in the figure) which communicates with the main flow passage 16.</p> |
