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Technical Reference section
Document code: SS1-UM-1.05
Checking the PAR calibration
Various techniques for checking the SunScan system PAR calibration and
consistency are described in the
Measurement Options, PAR calibration
section,
which you should refer to. This also includes advice on when to use the
recalibrate
and
restore factory calibration
procedures.
Factory calibration method
A standard PAR Quantum sensor provides the reference value of PAR that the Beam
Fraction sensor and the SunScan probe are set up to. This process is carried out
under a near-daylight spectrum lamp in controlled conditions.
Re-setting the factory calibration
The electronic components and photodiodes used in the PAR circuits of the Beam
Fraction sensor and SunScan probe are very stable and are not expected to change
for the lifetime of the instrument.
Circuit adjustment facilities in the Beam Fraction sensor are provided for the initial
factory set-up and are not intended to be used for routine adjustment thereafter. The
probe factory calibration cannot be adjusted without specialist equipment.
Warning! Do not attempt to change the factory calibration without referring back to
Delta-T first. The most likely cause of an apparent change of calibration is physical:
dirt in the grooves around the BFS diffusers, or dirt or staining of the probe diffuser.
If after checking the above you still have:
•
a Beam Fraction sensor with badly matched Total and Diffuse outputs, or
•
a SunScan probe with an out-of-spec calibration, or individual diode readings that
appear faulty,
please refer back to your agent or the factory.
