| dc.description.abstract | In this study, through a long-term outdoor test comparison of three different measuring of offset devices for sun-tracking, including PSD (position sensitive device), CCD (charge-coupled diode) and webcam, the results show a clear day, the amount of the deviation angle of three instruments are measured at approximately 0.2o-0.3o around, but in cloudy, the three instruments will be a slight difference, this time the PSD will be significantly less than the average deviation angle CCD and webcam, but this does not mean that the PSD measurement instrument to the average deviation angle is small so than CCD and webcam reliable cause of this difference is due to the low sunshine PSD unable to effectively discriminating position of the sun.
Overall PSD sampling speed, image processing is not required to determine the sun through the centroid position, but in the low sunshine and cloudy when not effectively determine the centroid position of the sun, CCD and webcam is possible through the optical lens and image processing to improve Looking for the accuracy of the centroid position of the sun, while the CCD can be changed due to different optical lenses and therefore taken out of the sun than the superior image quality clear advantage webcam, webcam in good times its low cost , in sunlight conditions can also stabilize the judgment deviation angle.
In addition, through PSD voltage meter to do with DR01 pyrheliometer correlation analysis, making the PSD in measuring the deviation angle measurement but also have the function of the amount of direct normal irradiation, PSD voltage conversion direct normal irradiation and DR01 pyrheliometer when measured after outdoor confirmed the average percentage error are less than 4%, there is a certain reliability.
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