A Yarn Irregularity Tester Using the Vibrating String Principle

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Abstract
A type of yarn irregularity tester is described in which mass per unit length of a moving yarn is determined by a method in which a short section of the yarn is auto matically maintained in resonant transverse vibration. The method makes possible a more direct determination of mass per unit length than is given by capacitance-type testers and leads to a calibration which is independent of the type of material being tested and the regain. The accuracy of the tester was examined by comparing its record with direct measurements of the mass per unit length of various yarns; the absolute agreement was very good. both for short-length (3 cm.) irregularities and mean count or linear density (over 1-m. lengths). In the former case worsted yarns from 22 to 88 tex (40's to 10's count) and having coefficients of variation (C.V.) ranging from 28% to 10% were measured with accuracies better than O.3% of C.V. In the determination of mean count of similar yarns the accuracy averaged 1%.