21
7. Calibration (Scale adjustment)
If the test piece fails in close contact
with the prism surface, remove it once
and again try to do same work after
carefully cleaning both the surfaces of
the test piece and the main prism with
tissue moistened with alcohol.
d)
While applying the light of the sample
illuminator lamp to the test piece
through its minor polished side, adjust
the lamp position (height) so that the
light penetrates into the test piece
through its minor polished side in
parallel with the main prism surface
(Fig. 7-3).
e)
While observing through the eyepiece,
gently turn the measurement knob to
set the scale indication approximately
to the Refractive Index shown on the
test piece (the upper scale is for
reading Refractive Index from 1.3000 to
1.7100, while the lower scale is for Brix
percent from 0.0 to 95.0%) (Fig. 7-5).
f)
Fig. 7-5
Refraction view
Scale view
Seeing the field of refraction view, the
colored boundary line is observed near
the intersection of the cross hairs. Turn
the
color
compensator
knob
to
achromatize the boundary line, and
stop turning when the boundary line
becomes neither reddish nor bluish.
Since reddish edge appears just above
the boundary line while bluish edge
appears just below it, the midpoint
where neither reddish edge nor bluish
edge appears indicates that the color is
completely compensated.
g)
