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ASD Document 600540 Rev. J 71 FieldSpec® 3 User Manual

www.asdi.com Chapter 7 Field Measurements

Step 2 Place the glass into the sink.

Step 3 Place 220 grade wet sandpaper onto the glass.

Step 4 Gently move the Spectralon reference in a figure 8 motion on the sandpaper,

using water as needed to wash away the thin layer that is sanded off.

Step 5 Blow dry with clean air or nitrogen or allow the material to air dry.

Step 6 If the material requires high resistance to deep UV radiation, the piece should

be prepared as above, then either of the following two treatments performed.

1 Flush the Spectralon piece with >18 milli-ohm distilled, deionized water

for 24 hours.

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.

WARNING! Do not use oils or soaps to clean the Spectralon white

reference.

7.11.3 White Reference Procedures

White references should be collected approximately every 15 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.

Note: 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 with the same

viewing geometry for a minute or two every few measurements. 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.

The FieldSpec spectroradiometer should be re-optimized for:

• Light changes.

• Any atmospheric changes.

• Temperature changes.

• Whenever accessory probes are changed.

Note: Environmental conditions can change rapidly or slowly. It all depends on

clouds, wind (affecting temperature), instrument warm up time, etc.

ASD FieldSpec 3 User Manual

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