A distribution apparatus and a method for delivering material, such as seeds,to adistribution area, such as a field to be planted, uses an automaticcalibration system. Theapparatus includes a frame supported for movement over the distribution areaand at leastone tank for containing the material to be delivered to the distribution area.At least oneload sensor monitors the weight of the at least one tank and the materialloaded therein. Adistribution system receives the material from the at least one tank anddistributes thematerial in a distribution operation. The distribution system includes ametering system tocontrol the rate of material flow according to a target rate. There is also acontrol unit forreceiving data from the load sensor with respect to the weight of the at leastone tank and thematerial loaded therein during the distribution operation. The control unitrecords the datereported by the load sensor, and processes the data to compare a load sensorderived changein weight (.DELTA.W L) with a theoretical change in weight (.DELTA.W T) basedon a calibration factor forthe metering system to determine if the metering system is operating at thetarget rate. Arate alarm warning is given if the calculated rate is outside of the targetrate and a revisedcalibration factor can be assigned to adjust the actual rate to equal thetarget rate.
