A popular method for measuring mass flows on combine harvesters is to register the induced force on a circular chute. Since this type of sensors are strongly subjected to wear and installed on difficult accessible places, it is important to know when the sensor provides wrong measurements without interrupting the process. In this study, a double, adaptive IIR notch filter is designed to track both resonance frequency and paddle rate of the feeding elevator on-line and providing a first rejection of both disturbance frequencies from the flow signal.