8. Calculate value of the standard turbidity solution at calibration point according to
following formula:
Tu
STD
= Tu
STK
*V
TOT
/(V
DW
+V
TOT
) = 49.38 FTU
Where:
Tu
STD
= turbidity of the standard solution (FTU)
Tu
STK
= 4000FTU – turbidity of the stock solution
V
TOT
= 100 ml volume of stock solution at calibration point (ml)
V
DW
= 8000ml - initial volume of distilled water
Note
: By using this formula and changing the volume of distilled water and Formazin
solution, you can prepare different calibration points for checking linearity of the turbidity
sensor or getting close to real turbidity value of standard turbidity solution.
9. After 5 minutes, remove the logger from the calibration container and wash the sensor
head under regular tap water.
10. Retrieve the data from the data logger as per the steps in the “Download” section on
page 19 of this manual. Make sure that a copy of the data is saved as well.
11. The calibration data should now be displayed in the Plot view. Click the Calibration tab
in the Properties view to the right of the Plot view.
12. Select the Tu sensor type from the drop-down menu. If the data logger has multiple
sensors, the Plot view will automatically update to only show the channel being
calibrated.
13. For the turbidity sensor, the Number of Samples field should be set to 25 samples.
14. Click on a stable point in the Plot view corresponding to the zero-turbidity calibration
point.
15. Click in the Real Avg field in the Calibration tab and enter the value 0.
16. Repeat steps 14 and 15 for the Formazin solution readings, entering the value
calculated in step 8 for the Real Avg field.
17. Follow the steps in Change calibration coefficients on page 27 to update the calibration
in the data logger.
November 5, 2010
Rev1.4
33
