EUTECH INSTRUMENTS DO 6, Instruction Manual, Page: 18 / 76

Instruction Manual DO 6
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In the mg/L (ppm) concentration calibration mode, barometric pressure, salinity
and temperature of the calibration sample needs to be set in the meter prior to
calibration. Since the pressure has already been set in the % saturation
calibration which is done earlier and assuming that the calibration is done on
the same barometric pressure and if you are using the temperature sensor in
automatic temperature compensation mode, you only need to input the known
salinity of the calibration sample to the meter. The dissolved oxygen mg/L (ppm)
concentration value can then be calibrated to the known sample concentration
calibration value. Note that the concentration calibration window is +/- 40% of
the factory default value. However the minimum point of calibration is 2 mg/L.
When you recalibrate your meter in % saturation mode, old calibrations in %
saturation will be replaced while the % saturation offset adjustment will be
erased. However, recalibration in the mg/L (ppm) concentration mode will only
replace the old calibration in the concentration mode and do not affect the
calibration in the percentage saturation mode.
To completely recalibrate your meter, or when you use a replacement electrode,
it is best to clear all calibration data. To erase all the old calibration data
completely, see Section 7.6 (rSt.5) Reset to Factory Default
4.2 Preparing the Meter for Calibration
Before starting calibration, make sure you are in the correct measurement mode
and in the correct calibration sequence. The temperature and the % Saturation
calibration must be done first before attempting to do the mg/L (ppm)
Concentration calibration.
In % Saturation, the meter is able to perform either a one point calibration or a 2
point calibration. For one point calibration, it is recommended that you perform a
100% Saturation calibration in saturated air. If you opt for 2 point calibration,
you can calibrate for 100% Saturation in saturated air and 0% Saturation using
a zero oxygen solution. The meter will take several minutes to reach 0%
Saturation value after submersion into the zero solution.
Rinse the probe well in the de-ionized (DI) water or rinse solution and wipe the
probe carefully taking care of the membrane.
Calibrate the meter in all the modes to ensure the highest accuracy throughout
the DO measurement range. In % Saturation calibration, should there be a