VNIR Training: Preparing Sample for Scanning

Soil Survey Research and LaboratoryNational Soil Survey CenterLincoln, NE

OverflowTray

Sample

MuglightSampleHolder

StrikeoffTool

SampleScoop

Brush

CannedAir

CleaningCloth

Clean puck window• Both sides• No streaks• No dust

When using canned airto 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 canduring spraying as thismay also dispense propellant.

Use quick, short bursts toclean all surfaces.

Mix/homogenize the sample.

Heap sample onto sample holder to overflow capacity.

Strike off sampleto level with top of sampleholder.

Soils consisting of largeparticles or OM may leave‘gouges’ or ‘tracks’ whenstriking off. Heap more soil onto the puck and re-strike.

Prepare leveled samplefor packing.

Support for puck window

Pack sample with equivalent of 46 lbsof pressure.Hold this for ~10 sec.Make sure piston isfree from ‘catching’ oninside of puck.

Brush away excess soil.

Since the muglight windowneeds to be clean to scanthe sample, riddingextraneous material at thispoint will somewhat reducethe 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 pistonshould be wiped clean Prevent contamination of The next packed sample.

Wipe the window of the

muglight free of dirt anddust just prior toplacement of the samplepuck.

Wipe the bottom of thepuck free of dirt and dustjust prior to placing iton the muglight .

Attentiveness is a high priority to avoid ‘bumping’soil out of the puck uponinsertion into the sturdyspring holding mechanismOf the muglight.

Oops!

The sample holder shouldbe placed flat on thesurface of the muglight,then gently, but firmly,slid into the springmechanism.

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 justprior to initiating a scan.

Canned or compressedair is good for removinglarge buildups, althoughone will still need to usea cleaning cloth for theremaining particulates.

Readings with thecontact probe are done onthe same packed sample inthe muglight sample holder. Make direct contact with the soil. Photo shows contactprobe 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 notperpendicular to the sample inthe puck. Therefore, the scanmay not be optimal.

By contacting the surface of thesample at a slight angle, theedge of the probe is more likelyto gouge the soil and stir it up,thereby negating the advantageof packing sample.