ISO 4291:1985 (R2020)

Establishes types of contact (stylus) instruments to be used, recommendations for their use, procedures for calibration of instruments and verification of their characteristics. Applies to a profile transformation, obtained under reference conditions. Departures from roundness of the measured profile, procedure, calibration and determination of systematic errors of rotation are dealt with in annexes A to D, respectively. Annex E gives rules for plotting and reading polar graphs. The position of the least squares centre can be calculated from a simple explicit equation given in annex F.