TM 10-4610-310-14
WP 0019 00
HIGH TURBIDITY MEASUREMENT
The meter covers a very wide range of turbidity values. For accurate measurements of samples exceeding 40
FTU's, the water must be diluted with correct amount of solution (HI 93703-0, or equal) or turbidity-free water
from the instrument case.
The volume of solution required to dilute the sample water can be calculated as follows.
V = 3000/T
Where,
V = volume of sample water [milliliter (mL)] to be combined with HI 90703-0 to obtain the final
volume of 100 mL.
T = Meter reading when 40 FTU's is exceeded.
Example, If Meter reading T = 200 FTU
V = 3000/200 = 15 (mL),
so, 15 mL of sample water is needed
100 mL - 15 mL = 85 mL,
so, 85 mL of HI 90703-0 is needed.
At this point, mix 15 mL of sample water with 85 mL of HI 93703-0 and measure turbidity.
The correct turbidity value of the original sample will be:
N x 100 (mL)/ V = A
Where
N=
new HI 93703 reading
A=
actual turbidity value , V = calculated in the previous example
Example, If the new reading N = 27 FTU
A = 27 FTU x 100 mL/15mL = 180 FTU. Therefore although the meter originally displayed 200
NTU's the actual turbidity is 180 NTU.
ACCURATE MEASUREMENT PROCEDURES
The following instructions will ensure accurate measurements:
1. Each time the cuvet is used, tighten the cap to the same degree.
2. Discard the sample soon after the reading is taken to avoid permanently clouding the glass.
3. All glassware used to contain the standards and the samples should be maintained with clean, washed
cleaning solution HI 93703-50, or equal. Rinse with calibration solution, HI 93703-0, or equal, or turbidity-
free water.
4. 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 before the analysis.
5. 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.
6. Before inserting a cuvet into the meter, wipe the cuvet with lint-free tissue, HI 93703-70, or equal. Handle
the cuvet so that no fingerprints can get on the glass areas where light passes (approximately 1 inch (2 cm)
from the bottom of the cuvet.
7.
Calibrate the meter monthly with calibration solution HI 93703-10, or equal, @ 10 FTU standard or
frequently for greatest accuracy. See WP 0048 00 for calibration procedure.
0019 00-3
