| 摘要 |
A secondary flow path is formed outside of a main flow pipe (42) that has a main flow path (43). An orifice (49) for constricting the flow of a gas is provided inside the main flow path (43). The secondary flow path consists of a pair of inlet flow paths (56) that are connected to the upstream side of the orifice (49), a second secondary flow path (59), the two ends of which are connected to the downstream ends of the inlet flow paths (56), a pair of discharge flow paths (57) that are connected to the downstream side of the orifice (49), a second secondary flow path (60), the two ends of which are connected to the upstream ends of the discharge flow paths (57), and a detection flow path (61), the two ends of which are connected to the center of the second secondary flow path (59) and the center of the second secondary flow path (60), and in which a flow sensor element (47) is disposed. The upstream end of the detection flow path (61) is positioned closer to the upstream side of the main flow path (43) than the two ends of the second secondary flow path (59), and the downstream end of the detection flow path (61) is positioned closer to the downstream side of the main flow path (43) than the two ends of the second secondary flow path (60).
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