Kipp&Zonen CNR 4 Net Radiometers - Manual (Page 28)

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3 CALIBRATION
3.1 Calibration of the pyranometers
The primary standard for pyranometers is the World Radiometric Reference. Reference pyranometers that are used
at Kipp & Zonen are calibrated using the primary standard.
The Kipp & Zonen pyranometer calibration is traceable to the World Radiometric Reference.
Further reference conditions are as follows: temperature 20 degrees Celsius, irradiance 500 Watts per metre square,
in the horizontal position. Each pyranometer has an individual calibration factor.
These factors can be found on the calibration certificate, included with the instrument and on the label applied on
the instrument itself.
3.2 Calibration of the pyrgeometers
There is no primary standard for pyrgeometer measurements.
The pyrgeometers in the CNR 4 are calibrated relative to the reference that is present at Kipp & Zonen.
In turn this reference has been calibrated against the World Reference at WMO in Davos
3.3 Recalibration of pyranometers and pyrgeometers
We suggest recalibration for all sensors, pyranometers, and pyrgeometers to be performed every two years by an
authorised Kipp & Zonen calibration facility, or as an alternative, by letting a higher standard run parallel to it over a
two-day period and then comparing the results. For comparison of pyranometers, you should use a clear day. For
comparison of pyrgeometers, you should compare night time results.
3.4 Checking the Pt-100 and Thermistor
Please check the reliability of the Pt-100 / Thermistor measurement by doing a parallel measurement with the other
temperature sensor. If this is not possible it can be done by temporarily attaching a stick-on type thermocouple to
the CNR 4's body, and then subsequently comparing the readout of the thermocouple with the readout of the Pt-100
/ Thermistor. The discrepancy, assuming that the thermocouple has a +/- 0.2 degrees accuracy, should be within
+/- 0.7 degrees. If it is greater, the deviating temperature sensor should be replaced.