Speaker
Description
Digital Metrology is undergoing a transformation as analogue, paper-based calibration certificates are replaced by machine-readable and machine-interoperable formats, like the Digital Calibration Certificate (DCC). This is especially advantageous in use-cases like the temperature calibration of thermography cameras, that need to deal with multi-dimensional measurement data recorded under a multitude of influence conditions and instrument settings. Machine-interpretable formats allow easy use of calibration data in subsequent processes and eliminate time-consuming and error prone manual transcription. Further, these DCCs enable direct upload onto the device’s controller, paving the way for internal transformation of measurement data, and automatized validation of calibration parameters.
The DCC is based on an XML file format that represents all the information of a traditional calibration certificate in a machine-readable and interpretable way, grouped under different harmonized elements. For instance, the administrative data element includes the description of the device under test, used transfer standards or calibration procedures, whereas in the measurement result section contains calibration results and their corresponding influence conditions. Details like integration time, active filters or a frame rate may also be referenced directly. Quantity values are expressed using the D-SI metadata model, which enforces an atomic pair of a numeric value and an SI unit, optionally accompanied by an expanded uncertainty, label or timestamp. Checking the content of a DCC against a predefined XML-schema guarantees data integrity.
Data inside a DCC can be clearly identified by machines (and humans) by labeling the XML elements with unique ids or keywords, so called “refTypes”. Creating an id and corresponding refId allows to link data entries within the DCC, e.g. a used calibration standard and the corresponding measurement result. Instead refTypes are labels for physical quantities, measurement condition, mathematical concepts and influence conditions, that are harmonized by the German Calibration Service (DKD) across 13 different committees, e.g. the refType basic_ambient marks an entry for environmental conditions inside the laboratory. These harmonized refTypes provide the basis for FAIR (findable, accessible, interoperable, and reusable) data management and internationally recognizable standards in terms of accessing DCC data.
We propose a first draft of a DCC for the radiance temperature calibration of thermography cameras, that is aligned with existing DKD expert reports for mass, contact thermometry, and best practices for radiation thermometry. The DCC will represent VDI 5585 calibration practices using either a single region of interest in the image center or additional regions in the image corners for determining the radiance temperature. The proposed draft will be open for discussion to assess further requirements and wishes from the community.
