| 摘要 |
PURPOSE:To accurately and easily detect a rotary number, by measuring the exhaust sound of exhaust air to perform frequency analysis and detecting the number of revolution of an output shaft on the basis of frequency showing the peak of the sound pressure level thereof. CONSTITUTION:The supply port of an air motor 6, wherein (v) pieces of vanes (not shown in the drawing) are fixed to an output shaft 7 through a rotor (not shown in the drawing), is connected to a compressed air supply source 3 and the exhaust port 4 thereof is connected to a sound arrestor 5 while a measuring apparatus 20 is connected to the microphone 15 arranged in the vicinity of the sound arrestor 5 and constituted of an amplifier 16, a band pass filter 17, an operation apparatus 18 and a display apparatus 19. Then, the frequency (f) showing the peak of the sound pressure of exhaust sound is calculated and the number of revolution (n) of the rotor is calculated from f=Kvn/60 [wherein K is an integer and (n) is rpm]. |
