LaMotte SMART 3 Electronic Soil Lab - Manual (Page 11)

SMART3 Soil 1.11 11
analyze this sample since a pinkish-red solution absorbs mostly green light.
REAGENT BLANK 
Some tests will provide greater accuracy if a reagent blank is determined to
compensate for any color or turbidity resulting from the reagents themselves. A
reagent blank is performed by running the test procedure on demineralized or
deionized water. Use sample water to SCAN BLANK. Insert the reacted reagent
blank in the colorimeter chamber and select SCAN SAMPLE. Note result of
reagent blank. Perform the tests on the sample water as described. Subtract
results of reagent blank from all subsequent test results. NOTE: Some tests
require a reagent blank to be used to SCAN BLANK.
COLORIMETER TUBES 
Colorimeter tubes which have been scratched through excessive use should
be discarded and replaced with new ones. Dirty tubes should be cleaned on
both the inside and outside. Fingerprints on the exterior of the tubes can cause
excessive light scattering and result in errors. Handle the tubes carefully, making
sure the bottom half of the tube is not handled.
LaMotte Company makes every effort to provide high quality colorimeter tubes.
However, wall thicknesses and diameter of tubes may still vary slightly. This may
lead to slight variations in results (e.g. if a tube is turned while in the sample
chamber, the reading will likely change slightly). To eliminate this error put the
tubes into the sample chamber with the same orientation every time.
The tubes that are included with the colorimeter have an index mark to facilitate
this. If possible, use the same tube to SCAN BLANK and SCAN SAMPLE.
METER CARE 
The optical system of the SMART3 must be kept clean and dry for optimal
performance. Dry the colorimeter tubes before placing them in the chamber to
avoid introducing moisture. For best results store the instrument in a area that is
dry and free from aggressive chemical vapors.