Alf Puettmer

Ultrasonic sensors for process industry

Continuous process monitoring in gaseous, liquid or melted media is a fundamental requirement for process control. Beside temperature and pressure other process parameters such as level, flow, concentration, and conversion are of special interest. More qualified information obtained from new or better sensors can significantly enhance the process quality and thereby product properties. Ultrasonic sensors or sensor systems can contribute to this development. The state-of-the-art of ultrasonic sensors and their advantages and disadvantages will be discussed. Commercial examples will be presented. Applications in the food, chemical, pharmaceutical industry and other are described. Possibilities and limitations of ultrasonic process sensors are discussed.

Miniaturized ultrasonic sensor system for liquid analysis

At the moment, known commercial devices to measure the sound velocity in liquids are limited in their application because the relation between velocity and concentration of substances is often not clear, for instance, if it is a parabolic curve. Additionally, the temperature dependence shows similar behavior. This contribution will present an ultrasonic sensor system consisting of a miniaturized multisensor arrangement for the comprehensive acoustic characterization of liquid mixtures. The sensor is based on segmented cylindrical piezoceramics and measures velocity, impedance coefficient, attenuation coefficient, and temperature. If it is a known liquid mixture it is possible to use the measuring quantities to calculate the material properties acoustical impedance and absorption or the concentration of selected substances in complex liquids. The sensor system is able to adapt itself to different and changeable absorption conditions which is typical of industrial processes. The measuring chamber is optimiz...