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Environmental measurement & analysis
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Solar Radiation & Photonic Sensors

Test facilities at EKO comply to the highest standards and are designed to test different sensor properties indoors and outdoors. EKO's calibration methods comply to the international standard procedures defined by ISO 9060 and are traceable to the international standards maintained at the designated national institutes. 


Calibration test facilities

Pyranometer calibration

The pyranometer is calibrated side by side against a calibrated reference pyranometer. Both pyranometers are horizontally mounted on a stable platform and connected to an accurate data acquisition system. The calibration factor is obtained by averaging at least 30 measurement series. Each series consist of the mean value obtained from 30 one-minute-averages. Only measurements above global broad-band irradiance of 400W/m2 are used.



   (Picture: MS-802 Calibration set up)

Pyrheliometer calibration

The MS-56 is calibrated under natural sun light against the EKO instruments reference pyrheliometer which is traceable to the World Radiation Reference (WRR) maintained at the World Radiation Center (PMOD) in Davos (Switzerland). Both MS-56 and reference pyrheliometer are mounted on a Sun Tracker to capture the direct solar radiation. The direct solar radiation is sampled at a rate of 1 minute over a period of more than 2 hours both in the morning and in the afternoon on a clear day. The calibration value of the MS-56 pyrheliometer is obtained by multiplying the sensitivity value [μV/W・m-2] of the reference pyrheliometer with the averaged ratio of the readings of both pyrheliometers (reference and MS-56). To improve the calibration accuracy and minimize the measurement uncertainty several operating criteria are applied.


  (Picture: MS-56 Calibration set up)

Spectroradiometer calibration check

On request EKO spectroradiometers can be characterized outdoors. The actual calibration of the MS-spectroradiometers is performed indoors against a NIST traceable tungsten-halogen OL-FEL standard lamp at a distance of 50 cm. The standard lamp has a known spectrum and the absolute irradiance is calibrated at several wavelengths. By measuring the spectroradiometer's detector responsivity in counts as a function of the irradiance at corresponding wavelengths, the sensitivility of each photo diode array pixel is converted into absolute units (W/m2/µm).


   (Picture: MS-700 Calibration check)

Indoors test facilities

During Research & Development state of the art test and measurement equipment is used to analyze the physical properties of radiation sensors.


Temperature dependency

Temperature dependency of the thermopile detectors is tested inside the climate chamber using an ultra stable AAA sun simulator (@ 1000 W/m2).


A special testjig is used to equalize detector temperatures and mimize stray-light reflections. Thermopile detectors are normally measured in the temperature range (-20 ... 50°C) but can also be measured in an extended range (-40 ... 60°C).    


The MS-56 First Class pyrheliometer and MS-802 Secondary Standard pyranometers are individually checked and adjusted to verify its specification. Other sensor models can be characterized on request.







   (Picture: Test jig for pyranometer detectors)


Non-linearity of thermopile radiation sensors can be measured with a common standard method using a stable 1000 W/m2 light source and chopper wheel. The total irradiated power at the detector surface can be precisely attenuated by changing the rotation speed of the chopper without changing the lamp power. The total flux per second can be attenuated in steps of 10% down to 0.




   (Picture: chopper wheel)    

Cosine error

The cosine and azimuth error  of all 180° FOV radiometer models can be anylized on the computer controlled goniometer optical bench. The angular rotation of goniometer can be set to make discrete steps of 0.1° in the range (Zenith +/- 90°, azimuth +/- 180°).


The MS-802 Secondary Standard pyranometers are individually checked to verify its specification. Other sensor models can be characterized on request.


   (Picture: Automated goniometer)