Campbell Scientific Kipp and Zonen CMP-Series Pyranometers - Manual (Page 20)

CMP/CMA series manual
Page 19
4.14. Non-stability
This is the percentage change in sensitivity over a period of one year. This effect is mostly due to
degradation by UV radiation of the black absorber paint on the sensing element surface. Kipp & Zonen
recommends recalibration every two years. However, for quality assurance purposes some institutes,
companies or networks may require more or less frequent recalibration. Please read the chapter on the
calibration procedure for pyranometers for more information.
4.15. Spectral selectivity
Spectral selectivity is the variation of the dome transmittance and absorption coefficient of the black
detector paint with wavelength and is commonly specified as % of the mean value.
4.16. Environmental
The CMP/CMA series are intended for outdoor use under all expected weather conditions. The
radiometers comply with IP 67 and their solid mechanical construction is suitable to be used under all
environmental conditions within the specified ranges.
4.17. Uncertainty
The measurement uncertainty can be described as the maximum expected hourly or daily uncertainty
with respect to the ‘absolute truth’. The confidence level is 95%, which means that 95% of the data-
points lie within the given uncertainty interval representing the absolute value. Kipp & Zonen
empirically determine uncertainty figures based on many years of field measurements.