Hanna Instruments HI 93703 - Manual (Page 6)

11 10
HOW TO ENSURE ACCURATE MEASURE-
MENTS
• Each time the cuvette is used, tighten the
cap to the same degree.
• Discard the sample soon after the reading is
taken to avoid permanently clouding the glass.
• All glassware used to contain the standards
and the samples should be maintained clean,
washed with HI 93703-50 cleaning solution
and rinsed with HI 93703-0 or turbidity-free
water.
• Collect the samples in clean glass or plastic
bottles, fit stoppers and perform the analysis
quickly. If unavoidable, store the sample in
a cool, dark place, but not for longer than 24
hours (the sample needs to be kept at room
temperature prior to the analysis).
• To obtain a representative sample, gently,
but thoroughly, mix it before samples are
taken. Do not shake (to prevent air bubbles)
and do not let the sample settle.
• It is recommended to monthly calibrate the
meter with the supplied HI 93703-10 @10
FTU* standard or more frequently for greatest
accuracy.
• Before inserting vials
into the instrument,
wipe them with HI
93703-70 soft, lint-free
tissue. Handle vials so
that no fingerprints can
get on the areas
where light passes (ap-
proximately 2 cm/1
inch from the bottom
of the vial).
If you experience any problems in taking mea-
surements, please contact your dealer or the
nearest Hanna Instruments Customer Service
Department.
* 1 FTU = 1 NTU * 1 FTU = 1 NTU
• Even though HI93703 covers a very wide
range of turbidity values, for very accurate
measurements of samples exceeding
40 FTU *, Standard Methods require dilu-
tion. In such cases, the correct amount of
HI 93703-0 or turbidity-free water to be
added to the sample can be calculated
as follows:
Vos = 3000 / T
where: Vos = volume of sample (mL) to be
combined with HI 93703-0 to
obtain the final volume of 100
mL.
T = HI 93703 reading (exceeding
40FTU*)
E.g.: HI 93703 reading = 200 FTU *
3000 / 200 = 15 mL (Vos)
15 mL (Vos)+85 mL (HI 93703-0) = 100
mL
At this point, take a sample of this solution
and measure turbidity.
The correct turbidity value of the original
sample will be:
T
n
x 100 mL / Vos = T
a
where: T
n
= new HI 93703 reading
T
a
= actual turbidity value of the original
sample