A method of determining a mass flow rate, volumetric flow and test weight of grain during harvesting operations. A sensor is disposed in the harvesting machine against which clean grain piles are thrown by the clean grain elevator flights. The sensor changes the direction of the clean grain pile such that each clean grain pile compresses into a substantially discrete, contiguous shape producing discrete grain forces resulting in discrete signal pulse magnitudes generated by the sensor. The mass flow rate is calculated by summing the signal magnitudes and dividing the summed magnitudes by the sampling period. The volumetric flow rate is calculated by multiplying the pulse width generated by the sensor by a multiplier which relates pulse width to volumetric flow. The test weight of the clean grain is calculated by dividing the mass flow rate by the volumetric flow rate.