Kipp&Zonen BSRN Scientific Solar Monitoring System - Manual (Page 54)

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Figure 4.9. Brusag two-axis active tracker. Active
tracking is accom plished by balancing the signals from
the quadrant sensor that is found on the flat of the
elevation disk. The pyrheliom eter is a Kipp & Zonen
CH1.
(3) The base on which the tracker is to be placed m ust be stable. W hile active trackers and som e
passive trackers are able to correct for a non-level surface, all trackers perform better if they
are m ounted such that the instrum ent base is level. Trackers m ounted on pedestals should
be levelled such that the vertical axis of the tracker, and not just the pedestal post, is
perpendicular to the horizon. A three-point base that allows easy adjustm ent is recom m ended.
The use of spring tensioners, lock washers, or bolts that are tightened using double nuts,
will reduce the problem of the connection between the m ounting post and the tracker base
loosening and causing the tracker to tilt from level. The tracker should be rotated about the
vertical axis during the levelling process to ensure that the axis is vertical. A num ber of active-
tracking and com puter-controlled passive tracking system s are capable of m athem atically
correcting for out-of-level conditions so that solar tracking is m aintained. These corrections,
however, do not correct for the tilt error of any pyranom eter or pyrgeom eter that is m ounted
Figure 4.8. A single-axis synchronous m otor tracker.
This m odel is an Eppley Model ST-1 Equatorial Mount.