9
Measurement and Calibration
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
”
.
Single measurement - 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 Measure icon begins flashing.
1.6 Wait for the reading to stabilize, the Measure icon will stop flashing.
Press the
Meas
key, the meter will take a measurement again.
Single measurement - high turbidity samples (>1100 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 =
Continuous measurements
3.1 Ensure that the meter is in the continuous measurement mode (Refer to page 8
“
Selecting the measurement mode
”
).
3.2 Fill the vial with the sample. Cap the vial.
3.3 Gently invert the vial several times to mix the sample.
3.4 Wipe the vial with the lint-free cloth to remove waterdrops and fingerprints.
3.5 Place the vial in the measurement chamber. Align the mark on the vial with the arrow on the meter.
3.6 Close the light shield lid. Press the
Meas
key, the Measure icon begins flashing, the meter continuously measures the sample.
To stop the measurement, press the
Meas
key again.
T
d
(V
s
+ V
d
)
V
s
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)
