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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:
http://oceanoptics.com/frequentlyaskedquestions/light-sources-radiometric/
Uncertainty Level Calculation for DH-3PLUS-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.
JCGM100:2008: GUM 1995 with minor corrections
355-00000-003-01
Calibration Basics
Appendix A
17
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