ISO 2648:2020

Overview

ISO 2648:2020 - "Wool - Determination of fibre length distribution parameters - Capacitance method" specifies a standard test method for measuring fibre length distribution in slivers and rovings produced from combed wool or combed synthetic fibres. The method uses a capacitive sensor to derive length-distribution parameters such as Hauteur (H) and Barbe (B) and their coefficients of variation (CV). The standard notes that it is not directly applicable to wool/synthetic blends because differing dielectric properties affect the capacitive measurement.

Key topics and technical requirements

• Scope & limitations
  • Applies to slivers and rovings from combed wool or combed synthetic fibres.
  • Not suitable for mixed wool/synthetic slivers due to different dielectric values.
• Measured parameters
  • Hauteur (H) - mean cross-section biased length (certifiable).
  • Barbe (B) - mean weight-biased length.
  • Coefficient of variation (CV) for H and B.
  • Additional outputs: L values, K values, percentage of short fibres, and tuft diagrams.
• Principle
  • A mechanical grip extracts a numerical draw; a test specimen (~30 000 aligned fibres) is formed and passed through a measuring condenser.
  • Change in capacitance as fibres replace air between condenser plates produces a cumulative Hauteur diagram.
• Apparatus
  • Mechanical grip (automatic or manual preparer).
  • Main capacitive sensor-based instrument with a measuring condenser (specified elongated geometry) and data capture (analogue recorder or digital system).
  • Test specimen holder, extractor, and restraining strip.
• Sampling and conditioning
  • Laboratory samples (e.g., sliver ~1.20 m) and detailed specimen-preparation procedures are specified.
  • Standard conditioning/testing atmosphere per ISO 139; typical preliminary conditioning period is 24 hours.
• Procedure & reporting
  • Clauses cover specimen preparation, measurement cycles (left/right ends), calculation methods for analogue and digital systems, and required test report elements.
• Precision
  • The standard includes precision data, within- and between-laboratory variation, and confidence intervals.

Practical applications and users

Who uses ISO 2648:2020:

• Textile testing laboratories performing wool fibre quality analysis
• Wool processors and combing mills for process control and acceptance testing
• Quality assurance and specification teams in yarn and textile manufacturing
• Instrument manufacturers and service providers for capacitive fibre-length analysers
• R&D groups developing fibre blending, carding and spinning processes

Practical benefits:

• Objective, repeatable measurement of fibre-length distribution for production control
• Data to inform spinning performance, yarn evenness and end-product quality
• Standardized reporting to support supplier specifications and quality agreements

Related standards

• ISO 139 - Textiles - Standard atmospheres for conditioning and testing (normative reference used by ISO 2648:2020)

Keywords: ISO 2648:2020, wool fibre length distribution, capacitance method, Hauteur, Barbe, capacitive sensor, sliver testing, roving measurement, textile testing.