The purpose of this part of ISO 10360 is to define metrological characteristics and methods for testing coordinate measuring systems (CMSs) using the principle of computed tomography (CT) as a single sensor which are dedicated to dimensional measurements of technical workpieces. This excludes medical imaging, medical dimensional measurements and as well non-destructive (material) testing applications of CT (e.g. defect analyses). The intention of this part of ISO 10360 is to achieve comparability with the characteristics of coordinate measuring systems with tactile and with optical sensors. The characteristics described in this part serve both for the specification of coordinate measuring systems using the principle of computed tomography and for the comparison between various coordinate measurement systems. This standard is intentionally dedicated to the CMS using X-ray-based computed tomography where the measurements are predominantly based on the attenuation contrast visible when penetrating physical matter. This standard may also be applied to CMS using other tomographic measurement principles based on a mutual agreement.
This standard covers coordinate measuring systems using sensors based on the kinematic/geometric principles of axial CT (fan and cone beam geometries) and as well helical CT as described in Annex F. This standard covers coordinate measuring systems and defines metrological characteristics and methods for testing which are intended specifically for non-gradient mono-materials which are homogeneous, i.e. cases where measurements of reference standards are performed which consist only of one (relevant) material which does not show a relevant lateral or spatial gradient in the attenuation of X-rays.
This part of ISO 10360 does not define metrological characteristics and related testing methods which are dedicated to measure the influence of surface roughness on CT-based CMS measurements (cf. e.g. [XXX], [YYY] for describing the potential influence). In close reliance on ISO 10360-2 and ISO 10360-5 and as well ISO 10360-8, this standard defines the methods for acceptance testing and for the monitoring of length measurement errors and probing errors when using CT-based CMS. Therefore, this document establishes the additional aspects necessary when using CT:
- Reference standards usable as alternatives to gauge blocks
- Comparability of the characteristics when using alternative standards (e.g. with spherical bounding surfaces)
- Comparability of the characteristics under different probing strategies (different number of points, degree of coverage of the elements to be measured)
- Definition of the characteristics for various operating conditions
- Notes on the treatment of affecting quantities such as environmental conditions, mathematical data filters and the nature of the measurement standard’s surface.