Calibration basics, Overview, Calibration for absolute irradiance – Ocean Optics Deuterium-Halogen Calibration Light Source User Manual
Page 14: Appendix a
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Appendix A
Calibration Basics
Overview
Calibrated systems, independent of the particular calibrated unit, are always traceable to national
standards. A calibrated item is comparable to all calibrated items which are calibrated for the same
calibrated unit.
Each measurement result has an uncertainty, and the level of uncertainty is given either for one single
standard deviation (k = 1) or for two standard deviations (k = 2), which is often named as expanded
uncertainty.
A calibrated device should give trusted results; therefore, the calibration has to be done by the metrologist
following a previously defined and proven calibration procedure. Clear documentation of the calibration
setup and of the calibrated devices used is an indispensable requirement.
Calibration for Absolute Irradiance
Absolute irradiance has the physical unit µW/nm/cm^2. The interpretation is as follows: This is the
wavelength resolved electromagnetic radiation which is emitted through an area [cm^2].
When you attach a cosine corrector correctly at the mounting of the light source then the amount of light
has a defined electromagnetic radiation power per surface area of your cosine corrector.
More detailed information can be found at:
Uncertainty Level Calculation for DH-3 plus-BAL-
CAL
Each realistic measurement has an uncertainty and therefore, a calibration has an uncertainty. The
uncertainty should be validated seriously since this reflects how reliable the calibration is. The following
international standards define the uncertainty and are describing how the uncertainty should be derived:
• IEC Guide 115: Application of uncertainty of measurement to conformity assessment activities in
the electrotechnical sector.