56
SECTION 5,
continued
2. The sample must have a flow rate or stirring rate that allows
for accurate probe performance. See Section 5.5.2 on
page 58. Make sure that no air bubbles are trapped in the
sensing area of the probe tip.
3. Press the DO key to make sure the meter is in DO
Reading mode.
4. Press the
CAL
key located in the lower left corner of the
keypad. The Cal icon will appear in the upper left corner of
the display.
5. Use the keypad to enter the concentration of the sample in
mg/L. The units will automatically switch from % to mg/L.
6. The instrument will ask for a salinity correction. If the sample
salinity is correct, press
ENTER
. If not, enter the value using
the numeric keypad. Press the
ENTER
to accept the number.
The stabilizing icon will appear while the meter completes
the calibration. When the calibration is complete, the meter
will return to the reading mode.
7. To end a calibration before it is completed, press the
EXIT
key
during the calibration sequence to back the display screen up
one at a time, then leave the calibration routine without
completing a calibration.
Note: If the
Cal
and
?
icons flash after calibration, the calibration failed
and meets to be repeated. See Error 6 in SECTION 8
TROUBLESHOOTING.
5.4.5
Calibrating a Sample to Read 100% Saturation
The sens
ion
156 Dissolved Oxygen meter can be calibrated to
read the dissolved oxygen in a water sample as 100% saturation.
Changes in the dissolved oxygen concentration of the sample
should be monitored using the % Saturation mode only, because
the concentration in mg/L will not be accurate.
1. Place the electrode in the sample deep enough to fully cover
the thermistor (metallic button) located on the side of
the probe.
