20
7. Calibration (Scale adjustment)
After wiping down the surface of the
main prism and test piece, apply a very
small amount of monobromonaphthalene
on the major polished side (the side
without indication of the Refractive Index,
see Fig. 7-4) of the test piece. If
monobromonaphthalene is applied too
much, it may cause error in calibration
and result in incorrect measurement.
Proper amount of monobromo-
naphthalene is one drop of 1mm in
diameter.
(2) Calibration with test piece
The test piece and monobromo-
naphthalene which are supplied as
accessories to the refractometer are used
for this calibration method.
b)
Open the secondary prism completely as
shown in Fig. 7-3.
a)
Fig. 7-3
Minor polished
side
Major polished side
Fig. 7-4
Light
Te st piece
Contact the major polished side of the
test piece evenly to the center part of the
main prism surface. At that time, set the
test piece so that its minor polished side
faces the reflactor. With contact of the
test piece to the main prism,
monobromonaphthalene spreads
between the test piece and main prism
as a thin film. If monobromonaphthalene
spreads out of the test piece, the amount
is too much. On the other hand, if it dose
not spread for the whole test piece, the
amount is too small. Don't press the test
piece to the main prism with fingers, etc.
If there is dust or foreign substance
between them, it may not only result in
incorrect calibration but also damage the
main prism surface.
c)
To Next Page
Loading...
Need help?
General
