55
SECTION 5,
continued
8. When the calibration is complete, the meter will return to the
reading mode. Press the
EXIT
key during the calibration
sequence to back out of the calibration routine, one screen at
a time, without completing a calibration.
Note: If the
Cal
and
?
icons flash after calibration, the calibration failed
and needs to be repeated. See Error 6 in SECTION 8
TROUBLESHOOTING.
To obtain a printout of the calibration conditions, use the meter
with the Docking station:
1. From DO Reading mode, press the
REVIEW
key.
2. Press
.
3. Press
EXIT
to return to the reading mode.
5.4.4
Calibration to a Known Dissolved Oxygen Concentration
The sens
ion
156 meter can be calibrated in a water sample of
known dissolved oxygen concentration. This procedure adjusts
for differences between this electrode method and an alternate
method such as a Winkler titration. These differences are most
prevalent in samples containing high concentrations of
dissolved substances.
High concentrations of dissolved substances can be corrected for
by entering a sample salinity value. However, salinity values may
not produce an adjustment equivalent to the value obtained by a
Winkler titration because various ions affect the dissolved oxygen
concentration differently.
The sample used for this calibration should be similar in
temperature and atmospheric exposure to the sample used for the
determination made by an alternate method.
To calibrate the meter against a dissolved oxygen concentration
determined by an alternate method:
1. Place the electrode in the sample deep enough to fully cover
the thermistor (metallic button) located on the side of
the probe.
