Recalibration Interval for Color/Trash Meters in Cotton Gins

Abstract

Because of drift, calibration of meters which measure cotton quality is essential for their accurate operation. The drift of High Volume Instrument (HVI) color/trash meters installed in a cotton gin was investigated so that a useful recalibration interval could be prescribed. Three meters recorded reference tile data at intervals of 30.0, 60.0, and 99.9 seconds for many hours in several different test runs. Comparisons of hourly means showed that measurements tended to be farther apart when the time between them increased, and that this pattern was fairly linear over a 24-hour period. Intercepts and slopes of the drift lines were used to select a recalibration interval for testing the data. Four-hour interval mean comparisons were studied to determine the percentages of differences which were within standard acceptable limits. Approximately 96%, 96%, and 100% of hourly-mean comparisons were within acceptable limits at the four-hour comparison interval for reflectance, yellowness, and trash, respectively.