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9.3.2 Measurement DO in static water
Power on the meter. Place the DO electrode into water. The water surface level should be higher than
the location of the temperature electrode. The angle for the electrode and water should be 45° to 75°.
Keep swirling the electrode in water slowly (>5cm/s) for 1 to 5 minutes. When the reading is fully stabilized,
record the measurement (do NOT stop the swirling while recording the measurement).
Never stop the DO electrode swirling in static water while measurement.
Otherwise, the dissvolved
oxygen will be consumed by the DO electrode and the reading will keep dropping.
9.4
Notes about DO Measurement
a)
When calibrating, the environment temperature and water temperature should be close to each
other (≤10˚C). If the difference is large, please dip the electrode into the sample water for about
10 minutes, then calibrate the electrode according to Section 9.2.
b)
Temperature has a large impact on DO measurement. When the electrode temperature and water
temperature have larger difference, the reading time must be greater than 3 minutes. Otherwise,
there could be some large errors.
c)
Salinity and barometric pressure also affect DO measurement. The meter has automatic salinity
compensation and manual barometric pressure compensation. For details, refer to Section 9.9.3.
d) When the meter is performing abnormally, please set the mode P7 to be
“
On
”
to restore meter
to factory default setting, and then do the calibration again before measurement.
9.5
DO Electrode Maintenance
9.5.1 Always maintain a moist sponge
Screw off the bottom lid of electrode calibration sleeve (
see picture 4-1), inspect whether the sponge
inside is moist. If it is dried out, please add in several drops of distilled water to the sponge to maintain
the satured air inside the calibration sleeve (Do NOT add too much water so it won’t be dripping).
9.5.2 Remove air bubbles
Inspect the
inner solution within the electrode membrane cap. Make sure it doesn’t have air bubbles. If
there are air bubbles, please screw off the membrane cap and add in new inner solution to remove the
bubbles. Then screw the cap back on.
