Hach Lange 2100AN, Instrument Manual

Page: 44 / 108

44
SECTION 3,
continued
3.3 Special Research Applications
Special features and operations have been designed into the 2100AN Turbidimeter
for special research applications. Refer to SECTION 10 on page 85 for more
information about application specific measurements, use of cell adapters, and
interchangeable filter modules.
Independent detector output selection and monitoring also is possible. For
example, if the back scattered light is needed to characterize a sample, the
information is accessed easily. Refer to Section 12.3.1 on page 96 for the
instrument diagnostic code number needed for a specific method development.
3.3.1 Ignoring Dilution Water
The turbidity of the dilution water can be ignored by pressing right arrow rather
than measuring the dilution water for the standard 00. The display shows
-----
.
Press the up arrow to advance to the next standard. 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.
3.3.2 Editing Calibration Data Points
Note: The calibration is based on a
first order linear equation consisting
of up to four 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. Using
Formazin standards other than
those specified in Section 3.2.3 on
page 37 may result in less accurate
calibrations.
When using Formazin standard dilutions other than the recommended 20-, 200-,
1000-, 4000- and 7500-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 a 25-NTU standard is placed in
the instrument instead of the 20-NTU standard, the 20.00 in the display is edited
to show the value of the new standard before the
ENTER
key is pressed to initiate
the measurement. Pressing the right arrow key accesses the editing mode causing
the decimal point to flash. Use the right arrow key to move the decimal point to
the appropriate location. Pressing
ENTER
accepts the new decimal location and
causes the
2
to flash. Because the
2
is correct as is, press the right arrow again to
ready the second digit for editing. The up arrow increments the flashing digit to
read
5
for the corrected display of
25.00
. Now, when
ENTER
is pressed, the display
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 Mode display (green LED) shows
02
.
Continue with the calibration, editing values any other substituted standards.