Analysis of Ultrasonic Correlation Flowmeters for Pulp Suspension

Abstraet-A transit time flow measurement system using ultrasonics and cross correlation is studied and constructed for use in the pulp and paper industry. The primary signals are produced by the modulation action of suspension particles on the intensity of two ultrasonic beams. Both continuous and pulsed intensities are used. The signals may be received either as attenuated beams penetrating the tube or as echoes scattered from the backwall. The intensity of the Doppler-shifted frequency of the scattered ultrasound is also used as a primary signal in order to avoid the ringing of the transmitted frequency within the crystal and pipe wall. The radial flow profile, the nature of the correlation method and the frequency filtering of the primary signals make the correlation function asymmetric and cause measurement errors. The system has been used for the measurement of pulp suspension in various cases, and some results are presented.