Hanna-instruments HI 93703 Manual de usuario descargar pdf (Pagina 10)

10

* 1 FTU = 1 NTU

• Even though HI93703-11 covers a very

wide range of turbidity values, for very

accurate measurements of samples ex-

ceeding 40FTU*, Standard Methods re-

quire dilution. In such cases, the correct

amount of HI93703-0 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 its 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

E.g. If T

n

= 27 FTU *

T

a

= 27 FTU *x100 mL / 15 mL = 180 FTU *

NOTE: Any sample taken above 1000 FTU will

show out of range by blinking "1000".

15

* 1 FTU = 1 NTU

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 calibrate the meter with

the supplied HI93703-10 @10 FTU* stan-

dard at least once a month or more frequently

for greater accuracy.

• Before inserting vials into the instrument,

wipe them with HI93703-70 or a soft, lint-

free tissue. Handle vials so that no finger-

prints get on the areas where light passes

(approx. the bottom 2 cm/1 inch).

If you experience any problems in taking mea-

surements, contact your dealer or the nearest

Hanna Customer Service Center.

SOURCES OF INTERFERENCE

• Presence of floating debris and coarse sedi-

ments which settle out rapidly will give false

readings.

• The infrared light source used for HI 93703-

11 turbidity meter, complies with the ISO

7027 International Standard and can effec-

tively minimize any errors due to colored

dissolved substances. This effect, called

"true color", is a common interference for

most commercially available instruments

operating in the range of visible light.

• Air bubbles and the effect of vibrations that

disturb the surface of the sample may give

false results and should be avoided.

• Dirty glassware could also affect readings

along with scratched or dented vials.

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