Preparation; Procedure; Dissolved Oxygen Calibration (Hi 98194, Hi 98196 Only) - Hanna Instruments HI 98194 Instruction Manual

7.3.1 Preparation

Appendix D – ACCESSORIES lists Hanna solutions used for ORP calibrations.
The calibration should be conducted at temperatures between 20-26 °C. The
sensor should be clean and oil free.

7.3.2 Procedure

• From the "Calibration" menu select "Single
param. calibration" and then "ORP calibration".
The display shows two options: "Custom ORP"
and "Restore factory calib.".
• For a user calibration select "Custom ORP".
• Fill a beaker with an ORP test solution (see
APPENDIX D "Accessories").
• Using the keypad, insert the numerical ORP
value and then press Accept to confirm.
• The stability counter will count down and the
message "Ready " and Confirm will be
displayed.
• Press Confirm to accept the calibration point.
• After confirmation, the following messages are displayed: "Storing" and
"Calibration completed".
• Press OK to return to the Calibration menu.
• Press Measure to return to the measurement screen.
• To restore the factory calibration data, select the corresponding option in the
"ORP calibration" menu and then press Select.

7.4 DISSOLVED OXYGEN CALIBRATION (HI 98194, HI 98196 only)

The accuracy of dissolved oxygen measurements is directly related to membrane
cleanliness and calibration technique. Oily coating and biological contaminants
are the primary cause of calibration drift in dissolved oxygen sensors. Unfortunately,
brushes or other cleaning objects may damage the membrane. Replacing the
membrane cap and electrolyte is the best way to perform periodic maintenance.
Although it may be easier to calibrate the D.O. sensor prior to deployment, it is
advised to calibrate at the site of deployment. Errors in measurement may result
if altitude and barometric pressure differ between the calibration and measurement
site. This is very important for autonomously logging probes.
Note Perform either the % D.O. Saturation or D.O. Concentration calibration.
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If the % D.O. saturation range is calibrated, the D.O. concentration range will
also be calibrated, and vice versa.
Dissolved oxygen concentration values are based
on % D.O. saturation, temperature, salinity and
atmospheric pressure. A standard solution or a
reference D.O. meter may be used to compare
readings during calibration.
The calibration of the D.O. concentration range
can only be performed at a single custom point (4 to 50 mg/L). It is recommended
to calibrate the D.O. sensor close to the values that will be measured.
Choose "DO calibration" from the "Calibration" menu, select the D.O. calibration
type using the arrow keys and press Select to confirm.
% D.O. saturation
The calibration of the % D.O. saturation range can be performed at a single or
2 standard points (0 % and 100 %), or at a single custom point (50 % to 500 %).
Procedure:
• To calibrate at 100 %, fill the calibration beaker
with approximately 4 mm (5/32") of water and
screw it onto the probe. The membrane should
not be wet. This condition corresponds to air
100 % saturated with oxygen and water vapor.
• The reading, temperature, calibration point and
the "Not ready" message are displayed.
• Once the reading has stabilized the countdown
timer will count down until the display shows
the "Ready" message.
• Press Confirm to accept the calibration point.
After confirmation, put the D.O. and temperature sensors into HI 7040L zero
oxygen solution and wait for stability to be reached. The stability timer will count
down and Confirm will appear. Press Confirm to store the calibration.
• 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.
Note The user can perform a single point calibration by pressing ESC after
the first point is accepted.
Note If the D.O. input is not within the acceptable range, the message "Invalid
input" is displayed.
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