Multi-Resonance Microwave Sensor for Moisture Monitoring: Review and Prospects

In this paper, the design of a novel multi-resonance microwave resonance sensor for moisture monitoring of pharmaceutical granulations is reviewed. This sensor allows a reliable determination of residual moisture directly in the production container. The reliably determinable measuring range could be extended from below 10% to at least 20% independent of other physical attributes and thus covers the complete moisture range typically occurring in fluid bed granulations. For this purpose, experimental prototypes with a novel electronic structure were developed. In order to enable the installation in the various granulators, prototypes with different dimensions of the sensor heads were realized. Within this publication, the measurement principle will be reviewed and prospects for the multi-resonance sensor will be provided.