EKO INSTRUMENTS CO., LTD. - Pyranometer MS-80 - Instruction Manual Ver. 3
6-2. Calibration and Measurement Uncertainty
It is recommended to recalibrate MS-80 pyranometer once every 5 years in order to verify the good quality of
the solar radiation measurements. Below explains about the calibration methods of EKO pyranometers and
their calibration uncertainty. For further information about recalibration and maintenance procedures, please
contact EKO or find on the EKO website (http://eko-eu.com).
1. Calibration Method
MS-80 is calibrated indoors against a 1000W/m
2
AAA class solar simulator radiation source and designated
calibration facility.
Indoor Calibration Procedure:
As the calibration procedure, 1) place both reference and production pyranometers in the center of the light in
horizontal position at the same distance from the solar simulator; 2) alternatively irradiate the reference and
production pyranometers with 1000W/m
2
continuously and measure the output (mV) from each pyranometer
for a specified time; 3) From the reference output (mV) and sensitivity (μV//W/m
2
), calculate the irradiance
(W/m
2
); 4) finally the sensitivity (μV/W/m
2
) value is calculated by division of the pyranometer output (mV) and
reference irradiance (W/m
2
).
Measurement Uncertainty of Indoor Calibration
The calibration uncertainty becomes smaller as the calibration is performed in a constant ambient
temperature and using a solar simulator with stable light source; hence the repeatability of indoor calibration
method is better than 99%.
The expanded calibration uncertainty depends on the pyranometer model, and its result is stated on the
calibration certificate.
The operation environment (such as ambient temperature) and solar simulator output are relatively stable,
the pyranometer calibration uncertainty is determined with consideration of uncertainty of the reference
pyranometer and maximum variation of incident light during the measurement of production pyranometer and
reference pyranometer.
2. Calibration Traceability
The Internal reference pyranometer maintained at EKO is traceable to the absolute cavity pyrheliometer
which is directly compared against the WRR (World Radiometric Reference) Primary Standard (Absolute
Cavity) maintained at PMOD (Davos, Switzerland). The logger system used for the calibration
measurement is traceable to JEMIC (Japan Electric Meters Inspection Cooperation).
Internal reference pyranometer is calibrated directly compared against the pyrheliometer, which is measured
against the EKO absolute cavity, and 2 units of internal reference pyranometers by Shading Method ([A New
Method for Calibrating Reference and Field Pyranometers (1995)] Bruce W Forgan) every one year.
EKO absolute cavity is directly traceable to WRR by comparing against WRR every 5 years.
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