The first error can be corrected within the allowed tolerance through the sensor calibration in the laboratory [3]. The second error, however, can only be minimized by aligning the wind direction sensor of the MM to the true north at the time of the installation of the MM [4, 5].The wind direction sensor’s accurate alignment of the north direction to the true north is not an easy job, particularly in circumstances where the MM is being installed. Great difficulties arise, particularly when the MM is built very high. In the http://www.selleckchem.com/products/Gefitinib.html Daegwanryung wind turbine test site, the height of the MM is 46 m. The installation of the long MM was accomplished by assembling its components on the ground, and then erecting the assembled mast from the floor (Figure 1). Although the exact alignment of the mast to the true north was done on the ground, the discordance with the exact north occurred during the process of erection and construction. Furthermore, the high elevation of the MM causes torsion, which generates the misalignment to the true north [6, 7].Figure 1.Meteorological mast erection using gin pole and winch.In this study, I propose a calibration technique to align to the true north to solve the discordance problem of the wind direction sensor. The misalignment of the tower to the exact north was corrected by measuring the accurate course of the wind direction sensor using the image taken by a camera, and simultaneously comparing it with the voltage value from the wind direction sensor. The blade section of the wind direction sensor from the image signal was separated by the segmentation method, and then the deviation degree was calculated by applying the least squares error method to the segmented image signal.We also performed an uncertainty analysis on the component error for the suggested method in a practical situation. An experiment applying the method on the MM at the Daegwanryung wind turbine test site was conducted and the validity of the method was confirmed.In the following sections the experimental setup of the proposed technique will be presented. Section 3 will present the process of evaluating the true wind direction from the camera image captured. In Section 4, some uncertainties and the accuracy of the proposed technique will be analyzed. This will be followed by the research conclusion in Section 5.2.?Experimental SetupThe organizational diagram of the total system, which was used at the Daegwanryung wind turbine test site, is shown in Figure 2. The basic principle of this technique is as follows: the real wind direction value, ��true was evaluated by the measurement of the rotation direction of the wind direction sensor using the camera at a certain time. At the same time the measured direction value, ��measured was measured by the output voltage from the sensor. Finally the degree of misalignment to the true north was calculated by comparing the value of ��true and ��measured.Figure 2.

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