The gravimetric feeder (Figure9-11) is a device that uses a belt conveyors as its transporting means. In the process of transporting the ingredient from the in-feed to discharge, the material weight is taken from the belt and transmitted to an electronic controller. The electronic controller adjusts a variable speed motor on the belt drive or adjusts a gate over the belt so that the belt discharges a preset rate of ingredient by weight. The sensor by which the weight is measured on the feeder belt may be load cell, a strain gauge, a pneumatic cell, or a differential transformer. The sensor signal, along with an analog tachometer or digital counting sensor on the belt idler pulley, gives the electronic controller the input necessary to control the rate of flow by weight.