White Reference Procedures - ASD FieldSpec 3 User Manual

www.asdi.com
WARNING!
7.11.3

White Reference Procedures

Note:
Note:
ASD.Document 600540 Rev. C
2 Vacuum bake the Spectralon piece at 75° C for a 12 hour period at a
vacuum of 1 Torr or less. Then purge the vacuum oven with clean dry air
or nitrogen.
Do not use oils or soaps to clean the Spectralon white
reference.
White references should be collected approximately every ten (10) minutes
and can be varied depending on whether conditions are changing rapidly or
not changing very much. The Spectralon puck should be used when
optimizing and taking a white reference measurement.
For best results, the Spectralon puck should be at the same distance and angle
from the foreoptic as the sample will be during measurements.
When saving reflectance data, point the probe at the Spectralon once every
few measurements for a minute or two with the same viewing geometry. If the
relative reflectance of the Spectralon is less than or greater than one, a new
white reference may be needed. If the relative reflectance of the Spectralon is
greater than one, re-optimization is recommended.
You can change the screen in the RS
DN mode without leaving real-time reflectance. This will give you an idea if
you are nearing saturation levels in any of the spectrometers. If you are
nearing a saturation level or your response has dropped off to a low level, then
you would want to re-optimize.
The FieldSpec spectroradiometer should be re-optimized for:
• Light changes.
• Any atmospheric changes or changes in temperature.
Environmental conditions can change rapidly or slowly. It all depends on
clouds, wind (affecting temperature), instrument warm up time, etc.
68
Chapter 7 Field Measurements
3
application to view the spectra in raw
FieldSpec® 3 User Manual