15
5. Measurement
Taking DO readings
During measurement, the probe can be:
• fully immersed in the solution
• partially immersed in the solution
Do not allow the probe’s membrane surface to touch any-
thing! The probe guard (the piece with holes fitted over the
end of the probe) protects the membrane; you should leave
this piece attached to the probe at all times.
IMPORTANT:
since the DO probe consumes oxygen
from the sample, the sample must constantly flow past the
membrane to achieve more accurate readings. You can use
a stirrer to accomplish this.
To take measurements:
1.
Rinse the probe well with deionized
rinse water or rinse solution.
2.
Select the appropriate measurement
mode. Press the MODE key
to toggle
between modes:
• %saturation.
• mg/l (ppm)**,
• date/time clock
3.
Dip the probe into the sample.
Stir the
probe gently to homogenize the sample.
Make sure that the sample is continuously
flowing past the membrane sensor.
4.
Note the reading on the display.
If the
READY indicator is switched on, it will
appear when the reading is stable.
See figure
5.
Press the key
to activate the backlit
LCD. This helps you read measurements
in dimly lit areas. The backlit display
automatically turns off 20 seconds after
releasing the key to conserve batteries.
5.1
A
A
Probe guard
**To select between mg/l and ppm units, see page 33.
The ATC indicator should appear in the lower right hand corner of the display.
If it does not, this indicates an error.
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