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# BS ISO 2971:2013 pdf free

BS ISO 2971:2013 pdf free.Cigarettes and filter rods一Determination of nominal diameter
The principle of measurement of the mean diameter of a shape having a convex cross section follows the generalization of ‘Barbier’s Theorem’, which states that the mean diameter of a section is equal to the arithmetic mean of the apparent (or projected) diameters of the section as it is rotated at equiangular intervals in the field of view. It is required that the section is rotated by an integer multiple of 180°.
NOTE The principle is demonstrated in Annex B.1.
This must have an uncertainty of no more than 0,01 mm and be suitable for the determination of the diameter of rod-like test pieces with a nearly circular cross section. A schematic diagram of such an instrument is presented in Figure 1 and three different implementations are described in Annex D.
The scanning rate of the instrument shall be such that no eccentric motion of the test piece parallel to the longitudinal axis, within the measurement area, shall affect the accuracy of the measurement of mean diameter.
The ratio between the scanning rate of the apparatus and the rotational speed of the test piece shall be constant and high enough to ensure that the measured diameter, as well as the minimum and maximum values, shall be determined with sufficient accuracy, despite the possible ovality of the test piece.
The length of the scan path shall be sufficiently greater than the maximum diameter to be measured to avoid errors due to test piece eccentricity. The test piece shall be scanned a minimum of 32 times during a half-rotation (180°) or 64 times during a full (360°) rotation.
NOTE The rationale for the required number of scans is presented in Annex B.2.
In accordance with the manufacturer’s instructions, position the test piece within the measurement area, as close as possible to the centre of the measurement area.
The test piece, or the measuring apparatus, shall be capable of being rotated around the rotation axis such that any eccentric motion of the test piece, relative to the plane of the measurement, remains in parallel with the plane of the measurement and perpendicular to the longitudinal axis of the test piece.
Adjust the instrument and/or feeding and rotational apparatus for the plane of the measurement to measure the required section of the test piece.BS ISO 2971 pdf download.

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