Special Research Applications (Not Recommended); Ignoring Dilution Water; Editing Calibration Data Points; Preparing Formazin Dilutions - User Selected - Hach 2100N Instruction Manual

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SECTION 3,
continued

3.3 Special Research Applications (Not Recommended)

3.3.1 Ignoring Dilution Water

3.3.2 Editing Calibration Data Points

Note: The calibration is based on a
first order linear equation consisting
of up to three independent
variables. Unpredictable results may
occur if standards other than the
recommended calibration points are
used. The factory suggested
calibration points are those
determined by Hach Company
chemists and engineers to provide
the best calibration accuracy. Use of
Formazin standards other than
those specified in Section
Section 3.2.3 Preparing
Recommended Formazin Dilutions
may result in less
accurate calibrations.
3.3.3 Preparing Formazin Dilutions — User Selected
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The turbidity of the dilution water can be ignored by pressing the
key rather than reading the dilution water for the S0 standard value. The display
shows "-----". Then, press the
Ignoring the dilution water is not recommended for most applications because it
may result in significant errors for measurements below 100 NTU. Use it only in
situations where you know your dilution water is particle free (<0.05 NTU).
When using Formazin standard dilutions other than the recommended 20-, 200-,
1000- and 4000-NTU standards during calibration, edit these data points as they
occur in the display in the calibration procedure to agree with the actual turbidity
of the substituted standards.
For example, if during the calibration procedure (refer to Section 3.2.4
Calibrating the 2100N) a 2.5-NTU standard is placed in the instrument in Step 5
instead of the 20-NTU standard, the 20.000 in the display is edited to show the
value of the new standard before the
the measurement.
Pressing the
RIGHT ARROW
point" to flash. Use the
RIGHT ARROW
appropriate location. Pressing the
and causes the "2" to flash.
Because the "2" is correct as is, press the
second digit for editing. The
for the corrected display of 2.5000. When the
counts down from 60 to 0 as the measurement is made and corrected to
compensate for the turbidity of the dilution water. The instrument automatically
increments to the next standard and the S2 annunciator lights. Continue with the
calibration, repeating the editing function for any other substituted standards.
Hach Company recommends using 20, 200, 1000 and 4000 NTU formazin
standards for calibrating the 2100N Turbidimeter. Other dilutions can be prepared
and used, but if problems occur when using these alternative solutions, use the
dilutions specified in this section.
Prepare Formazin dilutions from well-mixed, 4000-NTU stock solution as
specified in Section 3.2.3 Preparing Recommended Formazin and dilution water
as specified in Section 3.2.2 Dilution Water. Prepare Formazin dilutions to span
the entire range of the instrument. The following Formazin standards are
suggested: one in the range of 10 to 30 NTU, one in the range of 180 to 220 NTU,
one in the range of 900 to 1,100 NTU and one of 4000 NTU. Standards must have
a difference of at least 60 NTU. In addition, make a blank measurement using the
same dilution water used in making the Formazin dilutions, and enter as the S0
calibration point. Prepare standard solutions immediately before use, and discard
the standards when calibration is complete.
44
key to advance to the next standard.
UP ARROW
key is pressed to initiate
ENTER
key accesses the editing mode causing the "decimal
key to move the decimal point to the
key accepts the new decimal location
ENTER
RIGHT ARROW
increments the flashing digit to read "5"
UP ARROW
key is pressed, the display
ENTER
RIGHT ARROW
key again to ready the