DO700-en-GB_v2.3 3/15
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Dissolved Oxygen Water Sample Test
To measure moving water (water sample velocity of flow >5cm/s) insert the DO electrode into
the water. The water surface should cover the electrode’s thermistor (temperature sensor). The
recommended electrode orientation with regard to the water is a 45°to 75°angle. Move the
electrode around in the water and allow 3 to 5 minutes to take the reading.
To measure in static water: Insert the DO electrode into water, water surface should cover the
location of the electrode’s thermistor (temperature sensor), the direction for the electrode with
respect to the water is a 45°to 75°angle. Quickly stir the electrode in water at a speed >5cm/s.
Allow 3 to 5 minutes while taking the reading.
To test in slower flowing water: Use the first method above but stir the electrode faster in the
water.
Dissolved Oxygen Measurement and Calibration Considerations
The air temperature and water temperature should be within 10 degrees C, if the temperature
difference is greater, please immerse the electrode in the sample water for 10 minutes and then
calibrate.
After each start-up
,
the electrode must be polarized and a calibration must be performed; do not
turn the meter OFF (when in the DO mode, the default auto power off time is zero).
During DO tests, the temperature affects the measurement greatly. The electrode’s thermistor
should come in direct contact with the water sample
.
Please allow 3 to 5 minutes for the
thermistor to gage a stable temperature measurement.
DO measurements are also greatly affected by Barometric pressure. The DO700 meter has an
automatic Barometric pressure compensation function.
The DO electrode must not be left static in the test solution. Always stir the electrode in the
solution.
When measuring, remove air bubbles from the solution under test otherwise measurement
accuracy will be compromised.
Small air bubbles in the electrode’s electrolyte are acceptable; however larger bubbles must be
removed.
Keep the surface of the DO electrode moist to protect the cathode electrolyte. The supplied
storage sponge should always be kept moistened with water for proper storage.
The salinity electrode is installed in the DO electrode. Its surface is plated with a layer of
platinum (black) to reduce electrode polarization. This surface must not be rubbed or wiped
(clean by swirling it in water). Wash organic matter off of the surface with lukewarm water
containing detergent or use alcohol if necessary.
For any display abnormalities while measuring or calibrating, set the meter to its factory default
settings using parameter P7 (explained in next section). If abnormalities persist, the electrode
most probably needs replacing.
