54
SECTION 5,
continued
reading mode, add additional sodium sulfite and cobalt
standard solution to the anoxic solution. Otherwise, press the
EXIT
key to back up one display screen at a time and leave the
calibration routine without completing the zeroing procedure.
5.4.3
Calibration in Water Saturated Air
1. Secure the probe cable to the calibration and storage chamber
by wrapping cable through the bottom of the chamber lid
before filling with water.
Note: Avoid completely
filling the lower part of
the calibration chamber
with water.
2. Prepare the calibration and storage chamber by holding it
under water and squeezing it a couple of times to pull a small
amount of water into the lower chamber through the inlet.
Alternately, open the bottom of the chamber and insert a
water-soaked sponge.
3. Insert the DO probe into the calibration and storage chamber.
The tip of the probe must not be flooded with water or be
holding a drop of water on the membrane.
4. Allow at least ten minutes for the atmosphere in the chamber
to reach a steady state.
Note: Gently squeezing the lower chamber a couple of times to force
water-saturated air into the probe chamber will speed up
stabilization. Avoid squeezing liquid water into the chamber.
Note: Keep the DO probe at a uniform temperature. When holding the
probe, do not touch the metallic button on the side of the probe. The
button is a thermistor that senses temperature. An inaccurate
calibration will result if the temperature of the thermistor is different
from the probe membrane.
5. Press the DO key to put the meter in DO Reading mode.
6. Press the
CAL
key located in the lower left corner of
the keypad.
7. The display will show
100%
. Press the
ENTER
key. The
stabilizing icon will appear while the meter completes the
calibration.
