Apparatus (600) for monitoring a mass flow rate of harvested grain in a combination (300) having a clean grain elevator (40) that includes a clean grain elevator chain (42), comprising: a sensor surface (522)； a sensor (500) arranged to measure the displacement of said sensor surface； a plurality of vanes (100) mounted on said clean grain elevator chain (42)； a hub (620) mounted on said clean grain elevator chain (42), in which said hub (620) releases grain, and in which said released grain comes into contact with said sensor surface (522)； and processing circuit in data communication with said sensor (500), said processing circuit configured to estimate a grain flow rate based on a signal generated by said sensor (500), in which said processing circuit is further configured to distinguish a property pulse (720) from a plurality of vane pulses (710), said property pulse (720) being generated when the grain released by said hub (620) comes into contact with said sensor surface (522 ), said vane pulses (710) being generated when the grain released by said plurality of vanes (100) comes into contact with said sensor surface (522).Aparato (600) para monitorizar una velocidad de flujo másico de grano cosechado en una combinada (300) que tiene un elevador de grano limpio (40) que incluye una cadena de elevador de grano limpio (42), que comprende: una superficie de sensor (522)； un sensor (500) dispuesto para medir el desplazamiento de dicha superficie de sensor； una pluralidad de paletas (100) montadas en dicha cadena de elevador de grano limpio (42)； un cubo (620) montado en dicha cadena de elevador de grano limpio (42), en el que dicho cubo (620) libera grano, y en el que dicho grano liberado entra en contacto con dicha superficie de sensor (522)； y circuito de procesamiento en comunicación de datos con dicho sensor (500), dicho circuito de procesamiento configurado para estimar una velocidad de flujo de grano basándose en una señal generada por dicho sensor (500), en e
