A radio frequency sensor system comprising a housing defining a resonant cavity. Radio frequency probe(s) in the cavity transmit and/or receive radio frequency signals. A radio frequency control unit is in communication with the radio frequency probe(s) for determining one or more states of the radio frequency sensor system based on changes in the characteristics of the radio frequency signals. A machine learning system is in communication with the radio frequency control unit for identifying and developing transfer functions and calibrations based on the changes in the characteristics of the radio frequency signals and determining the one or more states of the radio frequency sensor system.