Measuring with Optical Dissolved Oxygen (DO) Probes 154
24.5.1. User Calibration at 100 % and % Saturation
Preparation
• Remove probe from process.
• Flush probe and cap with a jet of clean water.
• Inspect for scratches or voids in cap surface.
• Replace Cap as required.
• Shake any remaining solution off the probe. No droplets should remain on the DO sensing surface before
performing the calibration procedure.
•
Verify the controller’s barometric pressure reading with a reference meter. The pressure value can be adjusted
from the controller’s Technical Menu.
•
Verify the temperature is reading correctly. The temperature value can be adjusted from the controller’s
Probe Setting menu.
•
Go to Probe Setting in Channel Setup to set measurement mode (Meas.Mode) and measurement unit
(Meas.Unit). Select between:
` DO_%Sat (% saturation) with unit displayed in %Sat
` DO_Conc (Concentration) with unit displayed in mg/L or ppm
• Set the Salinity value if the probe will be exposed to ocean or brackish waters.
Procedure
1. Press CAL to enter calibration mode.
2. At prompt, with the password enabled, input the passcode.
3. The controller recognizes the currently selected measuring unit.
4. To calibrate at 100 % saturation (or 8.26 mg/L) suspend the probe in water‑saturated air.
This condition corresponds to 100 % air‑saturated water at the temperature of measurement.
5. Use of calibration beaker containing some water or moistened absorbent material is recommended.
Loosely screw the beaker onto the probe (first thread only).
6. Allow 15 minutes for the air inside the beaker to become water saturated.
7. Press CAL to enter calibration mode after this 15 minute interval has elapsed.
8.
Once the reading has stabilized the CFM virtual key is displayed. Press CFM to save the calibration point.
Exit and Next virtual keys are available. Pressing Exit saves a single point calibration.
9. Press Next to follow with second‑point calibration.
10. To calibrate at 0 % (or 0 mg/L), place the probe in the HI7040 Zero oxygen solution and stir gently for
2‑3 minutes. Dislodge bubbles that may adhere to the cap.
The controller automatically recognizes the 0 % (ppm) standard and the value is displayed on the LCD.
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