| 摘要 |
PURPOSE:To ease the restriction on an applied object and the applied environment by measuring the number of revolution of the object through the detection of the frequency of cyclical sound waves generated as the object rotates in the medium of a fluid or the fluid. CONSTITUTION:When a rotary blade 5 rotates at the number of revolution nHz, of a rotary blade wheel equipped with n pieces of identical rotary blades in axial symmetry, sound waves having a repeated waveform of a frequency nfH2 always propagated at any rest point in the medium thereof such as air and liquid. The sound waves are detected with a microphone 10 and the frequency of the repeated waveforms are counted with a counter 9 to measure the number of revolution of a rotating shaft 3. |
