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Calibration of Roughness Parameters

Working Group 5.15

Referenzsoftware für die Rauheitsmesstechnik


National metrology institutes supply reference standards that allow physical quantities to be traced to the SI units.

To ensure the comparability of the parameters and procedures defined in the "geometrical product specification" (GPS) standardization chain for the characterization of surfaces, artifacts as well as software are used as measurement standards.

In ISO 5436-2, type F software standards are defined. These standards are used to verify the algorithms implemented in measuring instruments for data analysis (such as filtering the shape from the geometry as a whole, and the calculation of statistic parameters).

Type F1 standards are reference data (so-called "soft gauges") in a data exchange format that is specified in the standard.

Type F2 standards are reference calculation procedures. Type F2 software standards are used to check the software of measuring instruments by entering the same data into both the measuring instrument software to be checked and into the reference software (e.g. F1 standards) and then comparing the results of the software to be checked with the certified results obtained by the reference software.

The metrology institutes of the United Kingdom (NPL), the United States (NIST) and Germany (PTB) supply industry with Type F standards. RPTB, the reference software used for roughness measurements at the Physikalisch-Technische Bundesanstalt, has been used for over ten years for roughness calibrations. The roughness analysis programs (i.e., the algorithms for separating the shape from the geometry as a whole and the calculation of the parameters) were written in platform-independent C and set up as modules.

The RPTB core modules are called up by a web interface set up according to the architecture of the Model View Controller (MVC), which comprises the following three entities:

  • data model,
  • view, and
  • program controller.

The operator uses a web browser to work with the RPTB programs. Via the http protocol, the web browser communicates with the program controller which sends the viewing programs that present of the results as tables and charts to the web browser of the client's computer. Web applications normally use database systems as models, whereas the model area of RPTB is represented by the data analysis programs.
RPTB is designed in such a way that it is available not only for internal use, but also as reference software on a server located at PTB's data center for worldwide use by external operators. The server can be accessed externally either via PTB's web pages or directly via: www.ptb.de/rptb.


Figure 1: The modules for the calculation of the roughness parameters and for the separation of the shape from the geometry as a whole of the roughness reference software are called up by a web interface which is designed according to the MVC architecture. Here, the model represent data analysis programs.