Overview
ISO 2971:2013 specifies a non-contact optical method for determining the nominal diameter of rod-shaped products with convex circular or oval cross sections - in particular cigarettes and filter rods. The standard defines how to measure mean, minimum and maximum diameters and to quantify ovality (out-of-roundness) or roundness using a non-contact optical gauging system.
Key topics and technical requirements
- Measurement principle: Based on a generalized form of Barbier’s theorem - the mean diameter equals the arithmetic mean of apparent diameters taken at equiangular rotations (integer multiple of 180°).
- Apparatus: Optical measuring instrument with an uncertainty of no more than 0.01 mm; system must support rotation of the test piece (or view) and maintain the longitudinal axis perpendicular to the measurement plane.
- Scan density: Minimum 64 scans per full (360°) rotation or 32 scans per half (180°) rotation to ensure accurate mean, minimum and maximum diameter detection.
- Calibration & standards: Use working calibration standards (properties given in Annex A) and follow manufacturer calibration procedures.
- Conditioning & sampling: Test pieces must be conditioned per ISO 3402 and samples should be statistically representative and free of visible defects.
- Expression of results:
- Diameter: expressed in mm to nearest 0.01 mm (based on ≥64 scans/full rev).
- Sample mean diameter (typically from at least 10 test pieces) to nearest 0.001 mm.
- Absolute/relative ovality and relative roundness with specified rounding conventions.
- Accuracy assessment: Repeatability and reproducibility guidance is referenced and linked to interlaboratory studies (see ISO 5725-2 and Annex F).
Applications and users
ISO 2971:2013 is primarily used for:
- Production and process control in tobacco manufacturing (cigarette and filter rod diameter monitoring).
- Quality assurance and acceptance testing in industrial and contract test laboratories.
- Instrument manufacturers and calibration service providers developing or validating non-contact optical gauging systems.
- Regulatory and compliance teams requiring standardized dimensional measurement methods.
Practical outcomes include routine diameter control for consistent draw and fit, identification of ovality issues linked to product defects (wrap, gum lines), and traceable reporting for supplier verification and product specification conformance.
Related standards
- ISO 3402 - conditioning atmosphere for testing tobacco products.
- ISO 5725-2 - determination of repeatability and reproducibility for measurement methods.
- Annexes in ISO 2971 provide further details on calibration standards (A), measurement principle and scan count (B), error sources (C), non-contact techniques (D) and alternative contact methods (E).
Keywords: ISO 2971:2013, cigarettes, filter rods, nominal diameter, non-contact optical measuring, diameter measurement, ovality, optical gauging, calibration, ISO 3402, ISO 5725-2.
