Reduction in grain loss of combine harvesters will increase the efficiency of harvesters and the net income of the farmer. Grain lost in the field may emerge as a weed in the crop rotation and harbor unwanted insects;A simulation model was developed for calculating the various components of loss and yield in the combine. Forward speed was determined for each day of operation. Yield, total area harvested, and losses were also calculated;Transducers were designed for measuring yield, walker loss, shoe loss and forward speed of a combine and a model of the combine was constructed in the laboratory for evaluating these transducers. Hardware for signal amplification and conversion was designed and constructed and software was developed for a single-board microcomputer which collected and displayed the variables measured;Measurement of these variables should help in the control of the combine harvester.