APOS Calibration Process

APOS has been supplying turnkey NIR measurement systems to the bioenergy and wood-based materials industries for over ten years. We probably have the largest database of NIR spectra and reference samples of woody materials and board coatings available worldwide. And continue to expand with every customer project – with anonymised data.

So, how does the APOS Calibration process work?

1. We check the customer’s material for compatibility with what we consider to be a suitable stock calibration. We record spectra of the material in our laboratory and compare them with our databases using an APOS’ built matching software.
2. If we find a suitable stock calibration, it is adjusted with some customer samples to achieve the “perfect fit”. If nothing compatible is found – the exception – we develop a new calibration. Extension and new development are methodically very similar.
3. APOS carries out a considerable part of the reference analysis itself with its own laboratory equipment, sample presses, etc.. In addition, APOS works together with other accredited laboratories that are regularly checked by us in ring tests.
4. In our laboratory or at the customer’s site, test samples of the material are now presented to an APOS NIR system and exactly this sample is analysed according to the classical (DIN EN) laboratory procedure. In the case of new calibrations this can involve several hundred analyses, in the case of additions only very few.
5. From these “pairs”, consisting of spectrum and reference analysis, the optimal calibration is developed after a spectrum pre-processing, a factor analysis and with PLS regression. This is tested several times, validated with real samples and loaded onto the system to be delivered. After the system is installed, it is tested again with reference standards to detect transport damage and with real samples for final validation.
6. After this step, the calibration process is completed, and the system goes into regular operation. There is no need to check the system during the year.
7. During annual maintenance, the APOS technician checks the status of the system with standards and real samples and corrects if ever necessary.