HF scientific Micro200BW Turbidimeter - 0 -1000 NTU - Manual (Page 43)

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MICRO 200 BW 0 - 1000 NTU (5/05)
Rev. 3.1
b. Standard Formazin Solutions
Calibration of this instrument is based on Formazin, a
material which is made by polymerization.
Calibration samples may be obtained by diluting Forma-
zin stock suspension using “Turbidity-Free” water.
Formazin stock suspension can be prepared by the user
(Reference Standard Methods For Examination of Water
and Wastewater) or a kit can be purchased from, HF
scientific, inc., Catalog No. 50040.
Each kit contains:
-- Instruction manual
-- 1 liter of 4000 NTU Stock Suspension
-- 1 Gallon (3.79 liters) turbidity-free water
-- 4 Sample cuvettes (28 mm)
-- 4 Light Shield Caps
-- Graduated Pipettes 1 ea. in 1 ml, 10 ml, &
25 ml
-- 1 Reference Standard
NOTE: When the prepared samples start to flocculate,
they are unreliable and fresh ones must be
made. This will occur more rapidly for the
lower value diluted suspensions.
2. Calibration Steps 0-1000 NTU Range (Also See
Section IV)
To meet stated accuracy it is advisable to allow both the
analyzer and sensor to come to its optimum operating
temperature, which can take approximately two hours.
After this point you can proceed with the following
procedure.
Standardization should be performed after after 1000
NTU (Full Scale) Calibration, although it is possible to
standardize at any time without performing a complete
calibration.
Although it is possible to calibrate at any combination
of the calibration points, to achieve the stated accuracy
use the following procedure.
Read these instructions in entirety prior to calibration.
Select calibration menu then:
1. Insert 1000 NTU Standard
2. Rotate the standard while observing the frequency
until the lowest reading is noted.
NOTE: Be prepared for the two least significant digits
to move about, this is normal.
3. Calibrate the analyzer with the 1000 NTU Stan-
dard by pressing the F4 key.
4. A sensor calibration is first performed which ad-
justs the sensor for lamp variations. Then the
frequency at the time of this selection is saved as the
calibration frequency for the 1000 NTU standard.
The frequency is displayed in the right hand col-
umn.
5. Insert the 400 NTU standard.
6. Rotate the standard while observing the frequency
until the lowest reading is noted.
7. Press the F3 key.
8. The frequency at the time of this selection is saved
as the calibration frequency for the 400 NTU
standard. This frequency is displayed in the right
hand column.
9. Insert the 100 NTU standard.
10. Rotate the standard while observing the frequency
until the lowest reading is noted.
11. Press the F2 key.
12. The frequency at the time of this selection is saved
as the calibration frequency for the 100 NTU
standard. This frequency is displayed in the right
hand column.
13. Insert the Reference Standard.
14. Rotate the Reference Standard to its index point.
15. Press the F1 key.
16. The frequency for the 0.02 NTU standard is saved.
This frequency is displayed in the right hand col-
umn.