LaMotte DO 4000 Dissolved Oxygen Meter - Manual (Page 12)

SATURATED WATER USING A CALIBRATION CHART
The saturated water calibration using a chart requires more careful
aeration and assumes the water is saturated after 15 minutes of
aeration. An aquarium pump or other bubbling equipment can be
used to aerate the sample. It is important the sample be saturated. If
bubbling equipment is not available, the sample can be vigorously
stirred with a magnetic stirrer for 2 hours.
1. Fill a 1 liter beaker with distilled or deionized water.
2. Aerate sample for approximately 15 minutes. Press the °C button to
turn the meter on. Record the temperature.
3. Use the Solubility In Water chart to determine the solubility of
oxygen at the sample temperature.
4. Use the Altitude correction chart to determine the altitude
correction factor.
5. Multiply the oxygen concentration (Step 3) by the altitude
correction factor (Step 4) to obtain the oxygen concentration of the
sample.
EXAMPLE: Sample temperature is 25°C; pressure is 642 mm Hg.
8.263 x 0.84 = 6.94 ppm O
2
6. Set “SALINITY COMP” and “SLOPE” knobs on meter to zero.
7. Keeping probe at an angle, slowly immerse the probe at least 3.5"
into the aerated sample. Tap the probe gently against the side of the
beaker to remove air bubbles.
8. Press “O
2
” button. Wait for reading to stabilize. Adjust the “slope”
knob until display reads concentration of the sample as determined
in Step 5.
NOTE: If readings are unstable, stir more rapidly to avoid oxygen
starvation at the membrane.
9. The meter is now calibrated and ready for use. See Testing on page
16 for instructions.
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