Hanna Instruments HI 9829 - Manual (Page 45)

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Note Note Note Note Note If the D.O. input is not within the acceptable range, the message “Invalid
input” is displayed.
Single point Custom % saturation calibration
• For a calibration at another known value place sensor and temperature probe
into the known solution and change the calibration value, press the
<Cal. point> softkey and select the desired point.
• To insert a different calibration value, press <Cal. point> and then <Custom>.
Insert the desired value using the keypad, then press <Accept>.
• When the reading is stable, the “Ready” message is displayed. Press
<Confirm> to store the calibration point.
• The following messages will appear: “Storing” and “Calibration completed”.
• Press <OK> to return to the “Calibration” menu.
• Press ESC twice to return to the main menu.
• Press <Measure> to return to the measurement screen.
D.O. concentration
Verify the barometric pressure, conductivity and
temperature reading are correct. Calibrate them
if necessary. To calibrate the D.O. concentration
range, a solution with known Dissolved Oxygen
concentration value is needed. The solutions used
to calibrate with should be determined
independently (for instance by Winkler titration). Place the D.O. sensor with
temperature sensor into the known solution.
• From the “DO calibration” menu, select the “DO concentration” option, insert
the known concentration. Allow the sensors to reach thermal equilibrium with
the solution. Stir or agitate if possible to keep fresh solution in front of the
membrane and press <OK>.
• When the reading is stable, the stability timer will count down and
<Confirm> will appear. Press <Confirm> to accept the value.
• When the messages “Storing” and “Calibration completed” appear, the
calibration is completed. To return to the “Calibration” menu, press <OK>.
• To return to the main menu, press ESC twice.
7.6 CONDUCTIVITY CALIBRATION
A conductivity calibration is used to adjust for variations in cell factors by
using a standard solution of known conductivity. Oily coating and biological
contaminants are the primary cause of calibration drift in conductivity sensors.
This type of fouling changes the apparent cell geometry, resulting in a shift in cell
constant. Before performing a conductivity calibration inspect the EC sensor for
debris or blockages. The EC electrodes are situated inside the two small channels