EKO INSTRUMENTS CO., LTD. - Pyranometers MS-802/802F/402/402F/602 - Instruction Manual Ver.13
Table 6-1. Maintenance Items -- Continued
To maintain the best possible
measurement accuracy, regular
recalibration of the pyranometer is
recommended. Contact EKO for more
details and requests for a recalibration
and maintenance service.
Due to natural aging of materials the
detector properties of the
pyranometer can change in time
which affects the sensor sensitivity.
6-2. Calibration and Measurement Uncertainty
It is recommended to recalibrate EKO pyranometers once every 2 years in order to maintain 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.
1. Calibration Method
EKO Pyranometers series are calibrated indoors against a 1000W/m
2
AAA class solar simulator radiation
source. During a calibration sequence, the incidence irradiance [W/m
2
] is alternately measured with the
reference pyranometer of the same model. The sensitivity figure of the production pyranometers is
determined by calculating the output ratio multiplied by the sensitivity figure of the reference model.
As the calibration procedure, alternately place both reference and production pyranometers in the center of
the light in horizontal position, at the same distance from the solar simulator and measure the output from
each pyranometer.
Measurement Uncertainty of Indoor Calibration
The calibration repeatability and precision will be very high since the measurement conditions such as
ambient temperature and solar simulator irradiance are very stable during the calibration sequence. The
repeatability achieved by the indoor method is better than 99%. The expanded calibration uncertainty
depends on the pyranometer model and is written on the calibration certificate.
2. Measurement Uncertainty
To estimate measurement uncertainties of pyranometers, some understanding of the physical properties of
thermo-electric sensors is required. A brief look at the instrument’s specification list gives an impression of the
many parameters that affect the radiation measurements. Fortunately all these individual error sources, which
have a small magnitude, will rarely affect the measurement at the same time. However, it is very difficult to
calculate the combined measurement uncertainty because it is nearly impossible to isolate the individual
measurement conditions to determine the corresponding errors. This illustrates the difficulty and complexity
of the measurement uncertainty calculation. Some practical guidelines to assess the measurement errors are
given next.
To Next Page
Loading...
Need help?
General
