Hanna Instruments LP 2000-11 - Manual (Page 5)

9 8
• Even though LP2000-11 covers a wide turbidity range, highly
accurate readings exceeding 40 FTU* require dilution as recom-
mended by the Standard Methods.
Use the formula below to calculate the amount of HI 93703-0 or
turbidity-free water needed for accurate dilution.
The total volume = 100 mL.
Vos = 3000 / T
where:
Vos = volume of original sample (mL) to be added to HI 93703-0
to obtain the total diluted volume of 100 mL.
T = LP2000-11 reading (exceeding 40 FTU)
E.g.: LP2000-11 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 diluted solution and measure its
turbidity.
The correct turbidity value of the original sample is derived by:
Ta= Tn x 100 mL / Vos
where:
T
a
= actual turbidity value of the original sample
T
n
= LP2000-11 reading of the diluted solution
E.g. If T
n
= 27
T
a
= 27 x 100 mL / 15 mL = 180 FTU*
Note: Any sample above 1000 FTU* will show out of range by blinking
“1000”.
* 1 FTU = 1 NTU
Note: Wipe the cuvet thoroughly with
HI 93703-70 or a lint-free tissue before
inserting it into the measurement cell.
The cuvet must be completely free of
fingerprints and other oil or dirt, par-
ticularly in the area where the light goes
through (approx. the bottom 2 cm/1").
• Place the cuvet into the cell and
check that the notch on the cap is
positioned securely into the groove.
• The mark on the cuvet cap should point
towards the keyboard.
• Press the READ key and the LCD will
display a blinking “SIP” (Sam-
pling in Process). The turbidity
value will appear after approxi-
mately 20 seconds.