TM 10-4610-310-14
0005 00
TURBIDITY METER OPERATION - continued
8. Place the cuvet into the cell. Check that the notch on the cap is positioned securely into the groove.
9. The mark on the cuvet cap should point towards the LCD.
10. Press the READ/⇑ key. The LCD will display a blinking Sampling in Process (SIP).
11. The turbidity value will appear after approximately 25 seconds.
12. The turbidity meter covers a very wide range of turbidity values. For very accurate measurements of
samples exceeding 40 FTU's, standard methods require dilution. In such event, the correct amount of
solution (HI 93703-0, or equal) or turbidity-free water to be added to the sample can be calculated as
follows:
Vos = 3000/T
Where Vos = volume of sample [milliliter (mL)] to be combined with HI 90703-0 to obtain the
final volume of 100 mL.
T = HI 90703-0 reading exceeding 40 FTU's.
e.g., HI 90703 reading = 200 FTU
3000/200 = 15 mL (Vos)
15 ml (Vos) + 85 mL (HI 90703-0) = 100 mL
13. At this point, take a sample of this solution and measure turbidity. The correct turbidity value of the original
sample will be:
Tn x 100 mL/Vos = Tn
Where Tn = new HI 93703 reading
Ta = actual turbidity value of the original sample
e.g., If Tn = 27 FTU
Ta = 27 FTU x 100 mL/15mL = 180 FTU.
Accurate Measurement
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. Calibrate the turbidity meter monthly with calibration solution HI 93703-10, or equal, @ 10 FTU standard or
frequently for greatest accuracy.
7. 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.
Sources of Interference
The following instructions should prevent any interference in accurate measurements:
1. Presence of floating debris and coarse sediment that settle out rapidly will give false readings.
0005 00-3
