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CALIBRATION
8.3. ORP CALIBRATION
There are two options available:
Custom ORP: The user can perform a single point calibration using a custom point.
Restore Factory Calib.: The user can restore the factory calibration if a new sensor has been installed.
Calibration is used to compensate for changes in the potential due to contamination of the sensing
surface and drift in the reference electrode.
Calibration is not typically required but it does establish a baseline that can be used for future
validations.
Note: ORP values are not temperature compensated and can change with temperature.
ORP values should be reported with the reference electrode used and the temperature. The
HI7698194-1 reference is a Ag/AgCl reference with Cl- activity equivalent to 3.5M KCl.
Procedure
Note: If the tutorial mode is enabled, press Tutorial and follow the messages on the screen.
1. Remove the shield from the probe. Rinse the probe with purified water.
2. Fill the calibration beaker 2/3 full with the ORP test solution with a known concentration.
3. Immerse the sensors in the solution. Raise and lower the probe several times then discard this
solution.
4. Fill the calibration beaker 2/3 full with the ORP test solution with a known concentration.
5. Slowly place the sensors in the solution. Dislodge bubbles that may adhere to the sensors.
6. Screw the calibration beaker completely onto the probe body. Some solution may overflow.
7. Wait a few minutes for the measurement to stabilize. Use the arrow keys to select “Custom ORP”
and press Start to start the calibration. A text box window will appear. Use the keypad to enter
the value of the solution at the current temperature. Press Accept to confirm the calibration point.
8. The stability counter will count down until the display shows the “Ready” message.
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