The objective of this study was to develop a flow model for grain combinesbased on the laboratory and field response of an impact based grain flow sensor. The grainflow model developed in this study is of first order with constant coefficients. A computercode was written to solve the model and to simulate the response of a yield sensor whoseresponse had been determined previously for various types of flow rate inputs both in fieldand laboratory experiments. The computer program for the simulation can alsocompensate for the time delay. The simulation results of the theoretical model suited wellto the experimental data and showed that the model effectively shows the input-outputrelationship of grain flow through a grain combine. This model could be used for periodicflow signals acquired from grain yield sensors. It was concluded that the model postulatedin this study could be further developed to determine the grain yield entering the combineusing the outlet flow rate measured by a yield sensor.