Hanna Instruments HI 9146-04 - Manual (Page 6)

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If the sample contains significant salinity or
if the measurement is taken at a higher
altitude than sea level, the read-out values
must be corrected (by taking into account the
lower degree of oxygen solubility in such
conditions - see below).
Set the altitude and/or the salinity before
calibration and taking mg/L measurements.
The meter will automatically compensate for
these factors.
% O2 SATURATION READINGS
The % O2 reading provides the rate of oxygen
saturation with reference to 100.0% at sea
level.
TEMPERATURE READINGS
The lower part of the display
will show the measured
temperature in Celsius
degrees.
Allow the probe to reach thermal equilibrium
with the sample before taking any measure-
ment. The greater the difference between the
ambient temperature and the temperature of the
sample, the longer it will take the probe to
acclimatized itself to the sample.
MEASUREMENT
Make sure the meter has been
calibrated and the protective
cap has been removed. Im-
merse the tip of the probe in
the sample to be tested and
ensure that the temperature
sensor is also immersed.
To display values in % satura-
tion, press RANGE.
For accurate dissolved oxygen measurements,
a water movement of at least 30 cm (12”)/sec
is required. This is to ensure that oxygen
depleted on the membrane surface is con-
stantly replenished. A moving stream will pro-
vide adequate circulation.
During field measurements, this condition may
be obtained by manually stirring the probe.
Accurate readings are not possible while the
liquid is stationary.
During laboratory measurements, the use of a
magnetic stirrer to ensure a certain agitation of
the fluid is recommended. This way, any errors
due to the presence of air bubbles on the
membrane surface are minimized.
For an accurate measurement, allow sufficient
time for thermal equilibrium between the probe
and the measurement sample (a few minutes
if the temperature difference is several de-
grees).
mg/L READINGS
The mg/L readings make it possible to read the
concentration of the dissolved oxygen directly
in ppm.
RANGE
SAMPLE
%
°C