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SECTION 3, continued
3.2.1 Cleaning Sample Cells
Cells must be extremely clean and free from significant scratches. The
glass used to make cells is easily scratched – manufacturing cells free of
minor scratches and other imperfections is difficult. However, minor
imperfections are effectively masked by applying silicone oil as
outlined in Section 3.1.1 on page 35.
Clean the inside and outside of the cells by washing with laboratory
detergent. Follow with multiple rinses of distilled or deionized water.
Allow cells to air dry. Handle cells only by the top to minimize dirt,
scratches, and fingerprints in the light path.
3.2.2 Orienting Sample Cells
Note: When orienting and matching cells, it may be more efficient to use the continuous
reading mode. The instrument performs continuous readings if the READ key is
pressed and held. As long as the key is held, the lamp remains on and the display is
updated every 1.2 seconds. The instrument cannot be used in continuous read mode
if the signal averaging mode is on.
Precise measurements for very low turbidity samples require using a
single cell for all measurements or optically matching the cells. Using
one cell provides the best precision and repeatability. When one cell is
used, an orientation mark (other than the factory-placed diamond) can
be placed on the cell so that it is inserted into the instrument with the
same orientation each time.
3.2.2.1 Orienting a Single Cell
When using a single cell, make an index or orientation mark on the cell
as follows:
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