HF scientific DRT-100B Research Turbidimeters User Manual
Page 15
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DRT-100B (5/00)
(C)
ELECTRONIC CALIBRATION USING HF SECONDARY STANDARDS OR FRESHLY PREPARED
FORMAZIN SOLUTIONS
Before calibration is attempted, it is important to note that all the calibration potentiometers (reference adjust, linearity,
span) are inter-related. That is, adjusting one will also affect the value of the other ranges slightly.
1.
Prepare, on the day of calibration, standards of 8 and 800 NTU using the dilution chart in this manual under
Section IV. A.
2.
Clean, with “Kimwipes” and windex, the reference standard and the 8 and 800 NTU standards.
3.
To locate the calibration potentiometers, remove one screw and loosen the other from the access cover and turn
it to the side.
4.
Set the range selector switch to the 1 range. Standardize the instrument as described in this manual under
Section III B. If your reference standard has never been indexed or if it is a new reference standard index it at
this time (review Section III. B., Reference Standard Indexing, in this manual).
5.
Set the range selector switch to the 10 range. Insert the 8 NTU standard. Note the reading on the digital
display.
6.
Set the range selector switch to the 1000 range. Insert the 800 NTU standard. Note the reading on the digital
display.
7.
Before making any adjustments remember that the calibration potentiometers affect each other slightly. Here
is an example calibration:
a)
Set range selector switch to the 1000 range. Insert the 800 NTU standard. Adjust span potentio-
meter (1000 range, 800 NTU standard) until the digital display reads 800 NTU +10 NTU.
b)
Then set the range selector switch to the 10 range. Insert the 8 NTU standard. Adjust linearity (10
range, 8 NTU standard) to make the 8 NTU standard read approximately 8 NTU on the digital
display.
c)
Re-standardize instrument.
d)
Repeat steps 5 & 6. If the 8 NTU standard is not 8 NTU +.1 NTU or the 800 NTU standard is not
800 NTU +10 NTU then repeat step 7 a thru d until the instrument reads the correct value for all
standards with no further adjustments required.