This test method is considered satisfactory for acceptance testing when the levels of the laboratories are controlled by the use of the same reference standard cotton samples because the current estimates of between-laboratory precision are acceptable under these conditions. If there are differences of practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, ensure the test samples to be used are as homogeneous as possible, are drawn from the material from which the disparate test results were obtained, and are randomly assigned in equal numbers to each laboratory for testing. The test from the two laboratories should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If a bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias.

Fibrograph measurements provide a relatively fast method for determining the length and length uniformity of the fibers in a sample of cotton in a reproducible manner.

Results of the Fibrograph length tests do not necessarily agree with those obtained by other methods for measuring lengths of cotton fibers because of the effect of fiber crimp and other factors.

Fibrograph tests are more objective than commercial staple length classifications and also provide additional information on fiber length uniformity of cotton fibers. The cotton quality information provided by these results is used in research studies and quality surveys, in checking commercial staple length classifications, in assembling bales of cotton into uniform lots, and for other purposes.

Fibrograph measurements are based on the assumptions that a fiber is caught randomly along its length.

1.1 This test method covers the measurement of the length and length uniformity of cotton fibers by use of photoelectric measurement. The test method is applicable to fibers taken from raw or partially processed cotton (up to card mat) or some types of cotton waste, but not to fibers from blends of cotton with other fibers or to fibers recovered from cotton yarns, fabrics or to 100 % systhetic fibers.

1.2 This test method is especially adapted for determining the length and length uniformity of cotton fibers by models of the Digital Fibrograph, hereafter referred to as Fibrograph.

Note 1—Instructions for the use of Manual and Servo Fibrograph Models were included in the text of Test Method D 1447 in 1971 and previous editions.

Note 2—For other methods covering the measurement of the length of cotton fibers refer to Test Method D 1440.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.