Non-invasive characterization of fluid foodstuffs based on ultrasonic measurements

The food industry can benefit from a highly sensitive, non-invasive, self-calibrating, on-line sensor for characterizing liquid or slurry in process vessels during mixing, settling, stationary, or flowing conditions by measuring the reflections at the fluid-sensor interface, sound speed, and attenuation of ultrasound to determine the fluid density and solids concentration. The sensor system was developed by staff at Pacific Northwest National Laboratory. The sensor transducers are mounted directly on the stainless steel wall and the pipeline wall becomes part of the measurement system. Multiple reflections within the stainless steel wall are used to determine the acoustic impedance of the liquid, where the acoustic impedance is defined as the product of the density and the speed of sound. The probe becomes self-calibrating because variations in the pulser voltage do not affect the measurements. By basing the measurement upon multiple reflections, the sensitivity of the measurement is significantly increased. (C) 2004 Elsevier Ltd. All rights reserved.