Option 1 of this test method for the determination of the degree of filament yarn entanglement, as measured instrumentally, is used for acceptance testing of commercial shipments; however, caution is advised because information on between-laboratory precision is lacking. Comparative tests, as directed in 5.1.1, may be advisable.

If there are differences of practical significance between the reported test results for two or more laboratories, comparative tests should be performed by those laboratories to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, samples used for each comparative test should be as homogeneous as possible, drawn from the same lot of material as the samples that results in disparate results during initial testing, and randomly assigned in equal numbers to each laboratory. Other fabrics with established test values may be used for this purpose. The test results from the laboratories involved should be compared appropriate statistical analysis and a probability level chosen by the two parties before testing begins, 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 must be adjusted in consideration of the known bias.

Option 2 for this test method is intended for use when the supply of yarn is limited.

The instrumental option of this test method is based on the total randomization of the entanglements in the yarn; therefore, the distance measured between the point of insertion of a pin in the middle of the yarn and the point at which an entanglement is encountered, by movement of the yarn or the pin until it is stopped at a preset level of force, is representative of the distance between two entanglements at some location in the yarn.

Entanglements are used frequently instead of twist to ensure the integrity of filament yarns. Such entanglements generally give somewhat less protection during weaving or knitting than twist, but with proper care, will perform quite satisfactorily.