A system and method of calibrating a meter of a product distributionmachine, such as an agricultural air seeder is shown. The system uses one orboth of optical and mass flow sensors to measure the product flow rate. Thesensors are used to measure mass flow rate during a calibration process whilethemachine is in use. To improve sensor accuracy during the calibration process,themeter speed is changed to change the product flow rate to a rate at which thesensor accuracy is increased.
