Acoustic viscosity sensors are mainly designed for use with coatings and continuous oil-condition monitoring. However, they can also be used to monitor other fluid products such as chocolate.

Chocolate is a non-Newtonian pseudoplastic material that exhibits low viscosity at high shear rates and high viscosity at low shear rates. Acoustic viscosity measurements on samples return the product of high shear viscosity and density as opposed to their ratio (returned by capillary methods.) Density was measured for these results at approximately 1.35 g/cm3 and assumed essentially constant for the milk and dark chocolates tested here.

What part of the results is most significant? BiODE's system is calibrated to mineral oils over temperature and viscosity ranges, but the sensor is so sensitive that even the non-Newtonian characteristics of mineral oils (normally assumed more predictable) are reported at sensor's shear rates. While the sensor is prebiased for the degree of shear thinning in oils, additional shear thinning is observed for chocolates and put to use in process and quality control.