9
Measurement and Calibration
Turbidity Measurement
An accurate turbidity measurement depends on good measurement techniques. Factors such as clean sample vials, positioning of vial in the
measurement chamber, covering the vial with the light shield lid, meter calibration, removal of bubbles, etc. For more information, please refer to
page 7
“
Measurement and Calibration Hints
”
.
Low turbidity samples (< 200 NTU)
For the low turbidity samples, we recommend using the same vial to perform the measurement and calibration.
1.1. Rinse the vial with approximately 10ml of the sample, capping the vial with the screw cap and gently inverting it several times. Discard
the used sample and repeat the rinsing procedure two more times.
1.2. Fill the vial with the sample. Cap the vial.
1.3 Wipe the vial with the lint-free cloth to remove waterdrops and fingerprints. Ensure that the outside of vial is dry and clean.
1.4 Place the vial in the measurement chamber. Align the mark on the vial with the arrow on the meter.
1.5 Close the light shield lid. Press the
Meas
key, the meter begins the measurement, the
icon shows on screen.
1.6 Wait for the reading to stabilize, the icon will automatically switch to
.
1.7 Press the
Meas
key, the meter will take a measurement again.
In the measurement process, press the
key. The measured value will be locked or unlocked.
High turbidity samples (>2000 NTU)
For the high turbidity samples, the solution must be diluted prior to measurement. The dilution water can be obtained by filtering deionized water
through a < 0.45µ m filter membrane.
2.1 Repeat steps 1.1 through 1.5 above and record the measured value.
2.2 Calculate the true turbidity of the original sample using the following formula.
T =
Where:
T
= Ture turbidity of the original sample
T
d
= Measured value
V
s
= Volume of the original sample (ml)
V
d
= Volume of the dilution water (ml)
T
d
(V
s
+ V
d
)
V
s
