Labsphere RSA-PE-20 User Manual

AQ-00073-000, Rev. 7 15
The sphere efficiency factors (
κ
) for a given sample are a function of many variables including
the spatial distribution of the energy reflected from the sample, the reflectance of the sphere
wall, the geometry of the sphere (location of ports, baffles, etc.) and the efficiency of the detector
itself. Proper measurement procedures make it possible to greatly reduce or eliminate the effect
of such factors on transmittance and reflectance factor measurements.
During the sample scan of a transmittance measurement, the transmittance (T
s
) of a non-scatter-
ing sample placed in the path of the sample beam affects the amount of energy entering the
sphere and reaching the sample reflectance port. The sample scan value S
T
of the ratio recorded
by the instrument is:
The value D
T
displayed by the instrument, however, is S
T
divided by the value B recorded in the
background correction curve:
Therefore, in a transmittance measurement of a non-scattering sample, the value displayed by
the instrument is simply equal to the transmittance of the sample.
In reflectance measurement for a double beam spectrometer, the standard positioned at the sam-
ple reflectance port during the uncorrected background measurement is replaced by another
sample of unknown reflectance
ρ
u
. The value S
R
of the ratio recorded by the instrument during
the sample scan is:
The spectral data displayed by the instrument is:
S
T
T
s
E
s
ρ
s
κ
s
E
r
ρ
r
κ
r
----------------------=
Eq. 3a
D
T
S
T
B
------
T
s
E
s
ρ
s
κ
s
E
r
ρ
r
κ
r
E
r
ρ
r
κ
r
E
s
ρ
s
κ
s
---------------------------------------T
s
== =
Eq. 3b
S
R
E
s
ρ
u
κ
u
E
r
ρ
r
κ
r
-----------------=
Eq. 4a

Labsphere RSA-PE-20 Specifications

General

Brand	Labsphere
Model	RSA-PE-20
Category	Laboratory Equipment
Language	English