Hanna Instruments HI 98713 - Manual (Page 10)

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M E A S U R E M E N T P R O C E D U R E M E A S U R E M E N T P R O C E D U R E M E A S U R E M E N T P R O C E D U R E M E A S U R E M E N T P R O C E D U R E M E A S U R E M E N T P R O C E D U R E
To take turbidity measurements, follow the next steps:
• Turn the instrument ON by pressing ON/OFF.
When dashes are displayed on the LCD, the
instrument is ready. On the secondary LCD the
current time appears, if selected in SETUP menu.
• Fill a clean, dry cuvet with 10 mL of sample up
to the mark, taking care to handle the cuvet by
the top.
• Replace the cap.
• Wipe the cuvet thoroughly with a lint-free cloth
to remove any fingerprints, dirt or water spots.
• Apply silicone oil on the cuvet and wipe with a
lint-free cloth to obtain an even film over the
entire surface of the cuvet.
Note: It is very important to oil the cuvet, espe-
cially for low turbidity values (< 1 FNU) to
hide the glass imperfections that can influ-
ence the reading.
• Place the cuvet into the instrument. Align the
mark from the cuvet with the sign on the instru-
ment case and close the lid.
Note: If you have a cuvet with orientation mark,
place the cuvet into the instrument with the
orientation mark aligned with the sign on
the instrument top.
HEATING THE SAMPLE
Use of heat to remove air bubbles, although very effective in some cases, should be handled with care
because it can alter the turbidity of the sample. When heating a sample, the volatile components
from the sample can vaporize, the suspended components can dissolve or the sample characteristics
can change.
Therefore, the heating procedure should be used with extreme care.
The best way is to use a warm water bath and immerse the cuvet with sample into the bath. Heat the
sample only until the visible bubbles are removed.
Note: Always cool the heated sample to the original sample temperature before measurement.
The heating procedure can be used in combination with vacuum or ultrasonic waves application for
a more effective air bubble removal.
When taking any turbidity measurements several basic rules should be followed:
• Use always cuvets without scratches or cracks because they can cause inaccurate readings.
• Cap always the cuvets to avoid spillage of the sample into the instrument.
• Close always the lid of the instrument during measurement.
• Keep the lid of the instrument closed when it is not used to prevent dust or dirt entering.
• Put always the instrument on a flat, rugged surface when taking measurements.
• Do not operate in direct sunlight.
• Do not use too much oil to prevent contamination of the optical system.