ASD Document 600540 Rev. J 82 FieldSpec® 3 User Manual
www.asdi.com Appendix B Reference Information
The signal-to-noise measurement increases with the square root of the number
of scans used in the averaging.
Note: The actual spectrum average will be a compromise between noise reduction
through spectra averaging and the time required for each spectra collection.
For instance, if you are using the instrument in the field to measure a large
number of samples, you will want a smaller number of spectra in the average
to decrease the collection time required. If you are collecting spectra in the
lab, you’ll want to increase the number of spectra in the averaging to obtain
the cleanest spectra possible.
B.1.7 What if I want to keep the same settings all day?
Even if you could keep the same settings for the integration time, gain value,
and offset value for the entire day, you probably wouldn’t want to.
Most of the measurements made by the instrument are ratios where such
values get cancelled out and become irrelevant.
It is far more important to keep the instrument from saturation and to ensure
the (baseline) white reference is fresh.
B.1.8 When do I use absolute reflectance?
It depends on how you are analyzing your data. An absolute reflectance most
likely will not be needed when using an accessory with its own light source.
It can’t hurt to use absolute reflectance. The difference between absolute and
relative reflectance is small for wavelengths less than 2000
nm.
Because relative reflectance relies on a physical (Spectralon) white reference,
you will see detect deviations from the absolute below 350-400
nm and above
2000-2500
nm.
B.1.9 How do I know the field-of-view that I’m using?
The field-of-view is labeled on the foreoptic that you use. The bare fiber has a
25 degree field-of-view.
When you are measuring radiance, it is important that the RS
3
application
software is using the correct field-of-view setting.
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