M. Kruse et Am. Steiner, A METHOD TO TEST THE RELIABILITY OF SIZE GRADING BY SIEVES IN SEED TESTING USING A STANDARDIZED REFERENCE SAMPLE, Seed science and technology, 22(2), 1994, pp. 349-359
Standards for the apertures of sieves as set by ISO and DIN cannot gua
rantee high accuracy of seed grading, because they consider only one s
ource of variation of grading, but they can significantly add to accur
acy and should be observed in manufacturing sieves. Calibration of gra
ding by a standardised reference sample includes all sources of variat
ion of the whole grading process and therefore should be used for test
ing actual grading performance. For this purpose glass beads are most
suitable to use as a standard reference sample, because they show cons
tant properties and a high resolution. To demonstrate the utility of t
he calibration of grading by a standardised referencde sample, results
of a comparative test as well as results of additional experiments ar
e presented. Different methods to establish standards for grading equi
pment are discussed and starting-points for improving accuracy of size
grading are presented.