Kipp&Zonen CM 4 Pyranometer - Manual (Page 4)

3
CALIBRATION CERTIFICATE
The calibration certificate supplied with the instrument is valid from
the date of first use. Even though the calibration certificate is dated
relative to manufacture the instrument does not undergo any
sensitivity changes when kept in the original packing. From the
moment the instrument is taken from it’s packaging and exposed to
irradiance the sensitivity will deviate with time. See also the 'non-
stability' performance (max. sensitivity change / year) given in the
radiometer specification list.