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.
