Calibration of Roughness Parameters

Reference software for roughness metrology

Most of the methods used to characterize and evaluate the surface quality with the profile method have been standardized in a series of international GPS (Geometrical Product Specification) standards. These standards describe nominal properties of stylus instruments, the methods and measurement standards used for the calibration of these instruments, the weighting and transmission function of the phase-correct filter used for the separation of long-wave and short-wave profile components, the surface parameters and all terms important for their definitions.
Unfortunately, almost all of these standards have ambiguous definitions or implementation of these definitions is not clearly described. As comparability of the measurement results plays a very important role in roughness metrology, checking of the function of the software used in the devices is very important. ISO 5436-2 defines two new measurement standards: measurement standards of type F1 are test data sets in a data exchange format defined by this standard, and the measurement standard of type F2 is the reference software against which the software in surface measuring instruments can be checked.
The software developed at PTB is used as reference software of type F2 in accor-dance with ISO 5436-2. The advantage is that a certified software is available for the determination of surface parameters in accordance with international standardization. This program meets the requirements of  ISO 12119 and the regulations for software quality assurance in metrology reference. Some ideas regarding realization of the software were explained on the occasion of the EUSPEN Conference in Turin in 2001 reference.
The program packet comprises the two libRPTB and libTPTB libraries written in AN-SI-C, and two RPTB_IDL and TPTB_IDL interfaces which use the DLMs (Dynamic Loadable Modules) to call the library functions from the user interface which has been created with IDL (Interactive Data Language). The reference software can read and process one-dimensional ASCII files with a header composed of two lines and type F1 data format according to ISO 5436-2. Implementation of the type F1 data format in the reference software is described in smd_description.pdf . The libRPTB function library contains reading and memory functions, error handling functions, filter functions, simple mathematical functions and functions for the calculation of surface parameters in accordance with   ISO 4287, ISO 13565-2 and EN 10049. The libTPTB function library contains all functions required to determine the depth of grooves with flat and rounded bottoms in accordance with ISO 5436-1.

to the evaluation software

The schematic diagram in Figure 1 shows the software’s functionality:

Figure 1: Schematic view of the functionality of the reference software