ABSTRACT

In 1996, cotton yield monitors were not commercially-available. To facilitate in-field yield variability research, a weighing basket was installed in a Case IH 2155 cotton picker. Data gathered with the weighing basket allowed generation of cotton yield maps containing one data point per second of machine operation. Following basket installation, a set of tests was planned to evaluate measurement system performance. Tests were designed to allow evaluation of the uncertainty expected in each individual yield measurement. System dynamic response was also evaluated. One important objective was to generate data representative of typical operating conditions, thus tests were conducted while the harvester traveled along the edge of a cotton field. Known flow rates were provided by pumping water into the weighing basket, and a turbine flow meter was used as a comparative reference. Step loads were applied to allow investigation of system response time requirements. Result reporting techniques were derived from the American National Standard for test uncertainty and common system analysis texts. According to test results, the uncertainty associated with any individual steady-state flow rate measurement could be expected to fall in the range of ± 0.4 lb/s (95% confidence). This corresponded with ± 480 lb seed cotton per acre (95% confidence) assuming a four-row picker configured for 40-in. rows traveling at 2 mph. Random uncertainty was dominant (±0.4 lb/s, max) when compared with systematic uncertainty (±0.04 lb/s, max), thus spatial averaging has potential to reduce uncertainty in yield measurements. Dynamic responsiveness was limited by filtering techniques used to reduce the effect of transients in basket weight versus time data. Rise time was used as the measure of dynamic responsiveness, and had a maximum value of 11 seconds when responding to a step load. The assumed 4-row harvester covers 0.01 acres in 11 seconds. Testing and result reporting methods used in this study can be modified for future use in performance testing of mobile, continuous-weighing flow rate measurement systems.