Response of a yield sensor to known grain flow variations was investigated under laboratory operating conditions through comparison with an electronic scale mounted on a test stand. The yield sensor had a quick response to sudden changes in corn flow. Based on total weight comparisons, the average percent error at constant flow rates was 2.1%. The error increased to 3.2% and 4.3% when step inputs and transients were applied, respectively. The overall accuracy was within the accuracy range (+/-4%) reported by the manufacturer while the maximum error was more than 5%. The flow rate range used in the calibration was the most important factor in achieving high accuracy. Because of the fluctuations in estimated flow rate, a single data point did not correlate well with the actual grain flow rate. Averaging over 4 to 6 s usually resulted in an el error less than 4%. When the flow rate varied more profoundly during steps and transients, approximately 10 s averaging was needed to maintain the accuracy in some of the tests. The effects of potential sources of errors (such as varying combine ground speed, changing crop conditions, and varying grain flow profile) also need to be considered to use the results of this study for field applications.