ALTANA Haze-Gard Dual - Manual (Page 45)

44
English
11.5 Notes
• For values of less than 10 %, the
measurement range is automati-
cally converted to a display with
two decimal places.
• During measurement, the mean
is taken across the illuminated
surface of the specimen. As it
cannot be assumed that the
optical properties are the same for
the entire surface of the speci-
men, we recommend taking
readings at several points on the
specimen and calculating a mean
value.
• There is little sense in taking
readings from dirty, scratched,
or otherwise damaged specimen
areas, unless you wish to obtain
the measurements as an indica-
tion of the extent of the damage,
e.g. measuring abrasion resis-
tance (Taber Abraser).
• Specimen surfaces must be as
plane-parallel as possible; a
wedge shape will deflect light.
• When taking comparative measu-
rements, note the specimen thick-
ness, since absorbance and
scattering increase in direct pro-
portion to thickness.
• Differences in reflection characte-
ristics may affect transparency
measurements. If specimens are
glossy on one side and dull on the
other, the same surface should
always be directed toward the
sphere aperture.
• Optical quality cuvettes with
plane-parallel walls and an edge
length of at least 50 mm can be
used to take readings on liquids
(Chapter 15).
• In practice, it may be important to
know whether scattering is caused
by internal scatterers or surface
structure. In these cases, surface
scattering can be eliminated by
immersing the specimen during
the readings in a liquid with the
same refractive index as the
specimen. Only bulk scattering
will then come into play.
11 Parameters