This paper describes the design and implementation of a Yield sensor utilizing electro-optic devices. The sensor combines emitters and detectors which are mounted on the conduit (duct or chute) of a harvester. As the cotton passes through the chute, it is illuminated by the emitters. The detectors which are positioned across the conduit detect the light pulses. The detection circuit then generates pulse train. The pulse count is relative to the mass of the cotton passing through the conduit. The cotton weight is displayed on the cab indicator and also stored on a recording media, together with the GPS position of the picker. The data can then be processed and displayed as a yield map.