Hanna Instruments HI 95724 - Manual (Page 11)

11
GENERAL TIPS FOR AN ACCURATE MEASUREMENT
The instructions listed below should be carefully followed during testing
to ensure best accuracy.
• For a correct filling of the cuvet: the liquid in the cuvet
forms a convexity on the top; the bottom of this convex-
ity must be at the same level of the 10 mL mark.
• Proper use of the dropper:
(a) to get good reproducible results, tap the dropper on the table for
several times and wipe the outside of the dropper tip with a
cloth.
(b) always keep the dropper bottle in a vertical position while
dosing the reagent.
• It is important that the sample does not contain any debris. This
would corrupt the reading.
• In order to avoid reagent leaking and to obtain more
accurate measurements, it s recommended to close the
cuvet first with the supplied HDPE plastic stopper and
then with the black cap.
• Each time the cuvet is used, the cap must be tightened to the same
degree.
• Whenever the cuvet is placed into the measurement
cell, it must be dry outside, and completely free of
fingerprints, oil or dirt. Wipe it thoroughly with
HI 731318 (tissue for wiping cuvets, see chapter
“Accessories”) or a lint-free cloth prior to insertion.
( a ) ( b )
14
VALIDATION PROCEDURE
Use the validation procedure to ensure that the instrument is properly calibrated.
Warning: do not validate or calibrate the instrument with standard solutions other than the Hanna
CAL CHECK™ Standards, otherwise erroneous results will be obtained. For accurate Validation and
Calibration, please perform test at room temperature: 18 to 25°C (64.5 to 77.0°F).
• Turn the meter on by pressing ON/OFF.
• When the LCD displays “724”, it is ready.
• Place the CAL CHECK™ Standard Cuvet A
into the holder and ensure that the notch on
the cap is positioned securely into the groove.
• Press ZERO and “SIP” will blink on the
display.
• After a few seconds the display will
show “-0.0-”. The meter is now zeroed and
ready for validation.
INTERFERENCES
• Positive error: - Bromine
- Chlorine dioxide
- Iodine
- Ozone
- Oxidized Manganese and Chromium
• Alkalinity above 250 mg/L CaCO
3
or acidity above 150 mg/L CaCO
3
will not reliably develop
the full amount of color or it may rapidly fade.
To resolve this, neutralize the sample with diluted HCl or NaOH.
• In case of water with hardness greater than 500 mg/L CaCO
3
, shake the sample for
approximately 2 minutes after adding the powder reagent.