Solids-concentration measurement and flow measurement of slurries and sludges using ultrasonic sensors with random data analysis

An instrument has been developed for on-line monitoring of suspended-solids concentration of slurries and sludges in hostile environments. A narrow and parallel ultrasonic beam, projected across the pipe diameter, interacts with the flowing sample, and the inhomogeneities present in the sample scatter the ultrasound, resulting in amplitude modulation of the transmitted beam. The average modulation index (depth of modulation) of the received ultrasound signal is shown to be a function of suspended solids-concentration, flow velocity and mean particle size. In a constant-velocity system, if the mean particle size remains constant, then the received signal will be proportional to suspended-solids concentration. A closed-loop system using a phase-locked loop is used to give good acoustic stability. This instrument could also be used for on-line monitoring of suspended-solids concentration in a variable-velocity system by compensating for the velocity changes using the cross-correlation techniques described in Part 2.