Patent ID: 7062963

Claim:
A flow velocity measuring device comprising a flow passage comprising: an internal space having a curved wall surface, an introduction passage connected to the internal space at one end of the wall surface tangentially to the wall surface, a discharge passage connected to the internal space at the other end of the wall surface tangentially to the wall surface, and a branch passage connected to the internal space at substantially right angle to a direction, in which the wall surface is curved, and a sensor element arranged in the branch passage or a flow passage connected to the branch passage, and wherein a fluid is introduced into the internal space from the introduction passage to branch into the discharge passage and the branch passage, and the flow velocity of the fluid taken out from the branch passage is measured by the sensor element, wherein at least two internal spaces are provided to be connected in series so that the fluid taken out from the branch passage connected to one of the internal spaces is conducted to the introduction passage connected to the other of the internal spaces.