HF scientific Micro200BW Turbidimeter - 0-100 NTU - Manual (Page 41)

MICRO 200 BW 0-10 & 0-100 NTU (05/05)
Rev. 3.4
Page 29
It is well known that diluted Formazin is unstable. If
Formazin is used to calibrate the instrument ensure that
a fresh stock suspension is used. Formazin stock sus-
pension can be prepared by the user (Reference Stan-
dard Methods For Examination of Water and Wastewa-
ter) or a kit can be purchased from, HF scientific, inc.,
Catalog No. 50040.
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.
5.3.2 Calibration Steps 0-10 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 10 NTU
(Full Scale) Calibration, although it is possible to stan-
dardize 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 Extended Setup menu then:
1.
Insert 10 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. (Full Scale) calibrate the instrument with the 10
NTU Standard by pressing the F2 key to high-
light "Press Up to Calibrate". Then press the
key.
4. A full scale calibration is performed which
adjusts the maximum gain of the instrument.
The NTU value and frequency are displayed on the
lower edge of the screen.
5. Press the key twice to return to the
Sensor Setup menu.
6. Select Normal Cal...
7. Press the F3 key twice to highlight the frequency
for Cal Point 3.
8. Press the . The frequency at the time of the
selection is saved as the calibration frequency for
the 10 NTU standard. This frequency is displayed
in the right hand column.
9. Insert the 4 NTU standard.
10. Rotate the standard while observing the frequency
until the lowest reading is noted.
11. Press the F2 key twice to highlight the frequency
for Cal Point 2.
12. Press the . The frequency at the time of the
selection is saved as the calibration frequency for
the 4 NTU standard. This frequency is displayed in
the right hand column.
13. Insert the .02 NTU Calibration Standard.
14. Rotate the Calibration Standard to its index point.
If the standard has not been indexed, see page 25.
15. Press the F1 key twice to highlight the frequency
for Cal Point 1.
16. Press the . The frequency for the 0.02 NTU
standard is saved. This frequency is displayed in the
right hand column.
5.3.3 Calibration Steps 0-100 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.
Read these instructions in entirety prior to calibration.
Select calibration menu then:
1. Insert 100 NTU Standard
2. Rotate the standard while observing the frequency
until the lowest reading is noted.
3. Press the F3 key twice to highlight the frequency
for Cal point 3.
4. Press the key. 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.
5. Insert the 40 NTU standard.
6. Rotate the standard while observing the frequency
until the lowest reading is noted.
7. Press the F2 key twice to highlight the Frequency
for Cal Point 2.
Menu
F3