The supersaturation in liquid as well as the mean particle size and solid content (also called as slurry, magma or suspension density) of solids can be monitored simultaneously by single frequency ultrasound. A concept of mathematical modeling based on the ultrasound velocity and attenuation measured with two sensors (one for liquid and one for solid state) has been developed and was proofed by experimental data at different temperature levels. The model structure is characterized by a minimized effort for the parameter identification and can be easily implemented. A turn-key probe with heated cage avoiding incrustations is presented to enable the exclusive investigation of the solution in dynamic suspensions. Examples for application of single frequency ultrasound probes as PAT tools are demonstrated by case studies for industrial urea suspensions and for sugar crystallization. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.