User Instructions

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CALIBRATION
For 100% calibration, water-saturated air is the simplest method (and recommended method). It
involves suspending the probe over a contained surface of water or moistened absorbent material. The
temperature element should also be inside the container. Under equilibrium conditions, the partial
pressure of oxygen in air-saturated water is equal to the partial pressure of oxygen in water-saturated
air; a probe calibrated in water-saturated air will correctly read the partial pressure of oxygen in water
samples.
Note: Performing the calibration in dry air will introduce an error because reference compensations
are based on air containing 100% relative humidity.
Place a moistened sponge into the bottom of the Hanna storage/calibration vessel, or place deionized
water into the bottom of the small bottle or flask, then suspend the probe into the vessel.
Warning: Do not tighten the calibration vessel on the probe thread as the water vapor will
become pressurized. If using water, verify the probe Smart Cap has not been moistened. Wait a
minimum of 15 minutes for the air to become saturated with water vapor.
Calibrating the probe over a large water surface, such as a lake or aeration basin used in wastewater
treatment should also suffice.
Air-saturated water can be produced by bubbling air into a water sample for a prolonged period. The
point at which the water is completely saturated is difficult to estimate so there is a risk of under or
over saturation (if the temperature changes).
Single Point Automatic Zero Calibration
Submerge the probe into HI7040 zero oxygen solution and stir gently for 2-3 minutes. Wait for the
temperature and probe values to become stable.
Press CAL. The calibration menu will be displayed.
Press DO to select the DO calibration. The meter will automatically recognize the 0% standard.
The DO calibration screen will be displayed and the standard 0% saturation (or 0 mg/L, depending
on the currently selected measuring unit), will be automatically selected.
When the reading is stable within the acceptable range, the CFM functional key is displayed.