Apparatus and method for controlling a vibratory feeder in a weighing machine

Apparatus and methods are shown for controlling a weighing machine in which product is fed into one end a vibratable pan of a vibratory feeder and is discharged from the other end, for example into a weigh bucket. In a first embodiment, the amplitude of vibration of a pan is measured and is compared to a desired amplitude. The measured amplitude is compared to a desired amplitude, and the amplitude of vibration is adjusted by modifying an input signal to a vibrator attached to the pan until the measured amplitude equals the desired amplitude. In a second embodiment, a mechanism is included to stop the loading of product into a pan when a predetermined amount of product has been discharged from a pan into a weigh bucket, and the weight of product in the pan is monitored as additional product is discharged into the weigh bucket Only a preselected additional weight of product is subsequently discharged into the weigh bucket. A third embodiment involves at least two pans arranged in series, and the weight of product in the downstream pan is determined and monitored. The measured weight is compared to a desired weight of product in the downstream pan, and the amplitude of vibration of the upstream pan is adjusted, as needed, in a closed-loop manner to feed more or less product into the downstream pan to establish and maintain the desired weight in the downstream pan.