Instrument for measuring fluid velocity and solid or liquid particle flow in a fluid or vacuum

摘要

A sealed chamber in the form of a thin pipe has a rigid membrane covering one end and a small microphone (bandwidth 100-18000 HZ) located at the other. The chamber is filled with air. Particles or fluid striking the outside of the chamber produce an acoustic signal at the microphone. The resultant microphone output is filtered by an electronic circuit leaving only the 200 Hz and 14 kHz components. The 200 Hz measures fluid velocity and the 14 kHz measures particle flow.