| 摘要 |
In order to reduce fouling substances contained in an airstream in piping from arriving at a sensor unit, and to decrease measurement errors of the mass flow rate and detection frequency of abnormal values in a thermal flow rate meter, this thermal flow rate is provided with a secondary passage (2) for taking in a portion of the airstream (30) flowing through a primary passage (124), and a measurement unit (310) in which a flow rate detection unit (602) is disposed for measuring the flow rate of the airstream flowing through the secondary passage (2). The shape of the measurement unit (310) projected onto an orthogonal plane orthogonal to the direction of flow of the airstream (30) has a length dimension defined in a first direction on the orthogonal plane and the thickness dimension defined in a second direction perpendicular to the first direction on the orthogonal plane, and forms a shape in which the thickness dimension is less than the length dimension. A widened part (2w) in which the passage width is great on the upstream side is formed in the secondary passage portion further on the upstream side than the flow rate detection unit (602). The widened part (2w) is formed in the wall surface side that partitions the secondary passage (2) in the first direction. |
