Gas Flow Measurement with Cross Correlation Functions of Ultrasonic Signals Taking Advantage of Artficially Generated Vortices

In spite of many advantages ultrasonic gas flow meters are not generally accepted in the market of flow measuring instruments. Most of them are operating with ultrasonic impulses using the principle of time-of-flight measurement. Vortex frequency measurements up to now don’t use ultrasound for the detection of frequency although the sensitivity can be increased up to ten times and analogue signal processing is very easy [1]. Cross correlation measurements with two ultrasonic barriers are only used in a few cases on account of difficult signal processing, misunderstood physics and nonlinear calibration. To consider even unsymmetrical flow profiles multi-path arrangements of ultrasonic sensors have been applied. These disadvantages can be avoided by the combination of cross correlation measurements with small artificially generated vortices.