31
SECTION 2, continued
2.4.3.2 Calibrating with User-selected Standards
For accuracy, use the same sample cell or four matched sample cells for
all measurements during calibration. Always insert the sample cell with
the same orientation.
1. Fill a clean sample cell to the line (about 15 mL) with dilution water.
Note: The same dilution water used for preparing the standards must be used in
this step.
2. Insert the sample cell into the cell compartment and close the lid.
Press
I/O.
3. Choose signal average mode option (on or off) before pressing
CAL.
The
SIGNAL AVERAGE key is not functional in calibration mode.
4. Press
CAL. The CAL and S0 icons will appear (the “0” will flash).
The 4-digit display will show the value of the S0 standard for the
previous calibration.
5. Press
READ. The instrument will count from 60 to 0 (67 to 0 if signal
average is on), measure the blank and use it to calculate a correction
factor for the lowest standard. If the dilution water is ³ 0.5 FNU,
“E1” will appear (see Section 2.4.2.3 on page 26 for more dilution
water information). The display will automatically increment to the
next standard. Remove the sample cell from the cell compartment.
6. Thoroughly mix the 10 to 30 FNU range standard, then fill a clean
sample cell to the line with the standard. Insert the sample cell into
the cell compartment.
7. The display will show the S1 icon (with the “1” flashing) and
20 FNU or the value of the S1 standard for the previous calibration.
8. Edit the standard concentration using the arrow keys.
9. Press
READ. The instrument will count from 60 to 0 (67 to 0 if signal
average is on), measure the turbidity and store the value. The
display will automatically increment to the next standard.
10. Remove the sample cell from the cell compartment.
11. Thoroughly mix the 90 to 110 FNU standard, then fill a clean
sample cell to the line with the standard.
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