Labsphere RSA-PE-20 User Manual

AQ-00073-000, Rev. 7 21
1. Perform a reflectance factor measurement of a given sample as described in the
operating procedures.
2. Replace the sample with a light trap. The reflectance of the light trap is approxi-
mately 0%.
3. Execute a sample scan to record the measurement data on the light trap.
4. Compute the corrected reflectance factor for the sample,
ρ
s
, as follows:
where:
ρ
r
= the reflectance value of the reference standard,
R = the sample data displayed on the instrument expressed in percent, and
Z = the data from the light trap measurement, expressed in percent.
Note:
This zero-correction procedure can also be used in conjunction
with a mask at the sample reflectance port to accurately measure the
reflectance factor of samples smaller than the sample port dimensions.
Operating Procedures for the RSA-PE-20 Accessory
The RSA-PE-20 accessory can measure reflectance factors at either 0° or 8° angles of incidence.
The angle of incidence is controlled by the sample holder configuration at the sample reflectance
port. You should keep in mind, however, that 8° hemispherical measurements will include the
specular component reflecting off the sample surface. Although calibrations using the 0° geome-
try are available on a custom basis, the standard calibrations at Labsphere are performed at 8
°.
If
your application requires NIST traceability, you should use a calibrated reflectance standard and
the 8° reflectance geometry.
Since any integrating sphere accessory acts as a signal attenuator, you should run scans at a
slower scan speed than in ordinary transmittance work without the accessory, or increase the
integration time if collecting data at a fixed wavelength.
8°/Hemispherical Reflectance Factor Measurements
Hemispherical reflectance measurements can be made on diffuse or specular samples - the pro-
cedure is the same. If you are measuring a specular sample, a specular reference standard, such
as a calibrated first-surface aluminum mirror, should be substituted for the diffuse reference
standard.
1. Secure the 8
°
reflectance sample holder over the reflectance sample port.
2. Load a calibrated or uncalibrated reflectance standard at the sample reflectance
port.
ρ
s
RZ–
()ρ
r
100 Z–
()
-----------------------=

Labsphere RSA-PE-20 Specifications

General

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