VNIR Training: Preparing Sample for Scanning Soil Survey Research and Laboratory National Soil Survey Center Lincoln, NE

Overflow Tray Sample Muglight Sample Holder Strikeoff Tool Sample Scoop Brush Canned Air Cleaning Cloth

Clean puck window Both sides No streaks No dust

When using canned air to clean, do not shake the contents of the can. The propellant is a hydrocarbon which may leave a residue that could adversely affect spectrometer readings. Compressed air delivered via an oil-less compresser is preferred.

Also, avoid tilting the can during spraying as this may also dispense propellant. Use quick, short bursts to clean all surfaces.

Mix/homogenize the sample.

Heap sample onto sample holder to overflow capacity.

Strike off sample to level with top of sample holder. Soils consisting of large particles or OM may leave ‘gouges’ or ‘tracks’ when striking off. Heap more soil onto the puck and re-strike.

Prepare leveled sample for packing. Support for puck window

Pack sample with equivalent of 46 lbs of pressure. Hold this for ~10 sec. Make sure piston is free from ‘catching’ on inside of puck.

Brush away excess soil. Since the muglight window needs to be clean to scan the sample, ridding extraneous material at this point will somewhat reduce the need to do so later.

A packed sample.

During the compaction process, some soil particles will cling to the surface of the piston. The face of the piston should be wiped clean Prevent contamination of The next packed sample.

Wipe the window of the muglight free of dirt and dust just prior to placement of the sample puck.

Wipe the bottom of the puck free of dirt and dust just prior to placing it on the muglight.

Attentiveness is a high priority to avoid ‘bumping’ soil out of the puck upon insertion into the sturdy spring holding mechanism Of the muglight.

Oops!

The sample holder should be placed flat on the surface of the muglight, then gently, but firmly, slid into the spring mechanism.

The powerful spring can make it seem the samples holder is in place, when it is not. Observe the gap indicated by the orange arrows.

Complete downward placement of the sample holder is essential. Observe the gap indicated by the orange arrows.

If using the contact probe, clean the window just prior to initiating a scan. Canned or compressed air is good for removing large buildups, although one will still need to use a cleaning cloth for the remaining particulates.

Readings with the contact probe are done on the same packed sample in the muglight sample holder. Make direct contact with the soil. Photo shows contact probe approaching the sample before scanning. Note operator’s hand position…

In this photo, the operator is holding the probe farther towards the end of the handle. This makes it more difficult to hold the probe steady and to keep it perpendicular to the soil, which must be done to ensure a good scan.

The probe in this photo is not perpendicular to the sample in the puck. Therefore, the scan may not be optimal. By contacting the surface of the sample at a slight angle, the edge of the probe is more likely to gouge the soil and stir it up, thereby negating the advantage of packing sample.