Apparatus, systems and methods are provided for monitoring yield while harvesting grain. Grain released from paddles on the clean grain elevator chain of a harvester contacts a flow sensor (500) which reports the rate of grain flow through the clean grain elevator (40). A cleaning apparatus (200) driven by the clean grain elevator chain (42) is disposed to contact and remove material from the sensor surface (522). Processing circuitry in data communication with the sensor (500) is configured to estimate a flow rate of grain based on a signal generated by the sensor (500) and to distinguish a cleaning apparatus pulse (720) from a plurality of paddle pulses (710), said cleaning apparatus pulse (720) being generated when said cleaning apparatus (200) contacts said sensor surface (522), said paddle pulses (710) being generated when grain released by said plurality of paddles (150) contacts said sensor surface (522).
