HACH LANGE 2100N, User Manual

Page: 18 / 46

7. Push RATIO to
select Ratio on or off.
Ratio must be on for
Gelex standards
greater than 40 NTU.
For the 0–2 and
0–20 NTU Gelex
standards, select the
Ratio function that the
instrument will operate
in.
8. Put the 0–2 NTU
Gelex vial in the sample
cell holder with the
triangle on the vial
aligned with the
reference mark on the
sample cell holder.
Close the cover.
9. Read the value
when stable. Remove
the vial from the
instrument.
10. Record the value
on the white diamond
space on the vial using
a water soluble marker.
Record on the vial if
Ratio was on or off
when the vial was
measured.
11. Do steps 7–10 for
the other Gelex vials
(but not the stray light
standard). Measure
from lowest to highest
NTU.
Calibration verification
At intervals, measure the Gelex secondary turbidity standard that is
closest in value to the turbidity range to be measured. Do the steps in
Measure the Gelex secondary turbidity standards on page 15, but do not
change the value that is recorded on the vial.
Turn Ratio on if the Gelex vial is greater than 40 NTU. Select the Ratio
setting recorded on the Gelex vial for vials less than 40 NTU.
If the measured value is within ±5% of the value recorded on the Gelex
vial, calibration is verified. If not, calibrate the instrument.
Note: The StablCal ® primary turbidity standards can also be used to do a
calibration check. Prepare the StablCal vials before use. Refer to Prepare the
StablCal standards on page 11. Do not use the < 0.1 NTU StablCal vial as it does
not have an accurately identified NTU value. The instrument is calibrated if the
measured value is within ±5% of the StablCal value.
Optical system check
At intervals, measure the Gelex stray light standard to inspect the
integrity of the optical system. Do the steps in
Measure the Gelex stray
light standard on page 14, but do not change the value that is recorded
on the vial.
If the value measured is similar to the value recorded on the Gelex stray
light standard (within ±0.02 NTU), the instrument works correctly. If not,
contact Customer Service.
Prepare a sample cell
Use a clean sample cell(s) for sample measurement.
Note: As an alternative, a flow cell can be used for sample measurement. Refer to
Using a flow cell on page 28.
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