LaMotte DO 6 Dissolved Oxygen Meter - Manual (Page 14)

4 CALIBRATION
4.1 Important Information on Meter Calibration
Your meter has three measurement modes namely the DO % saturation
measurement mode, the DO mg/L (ppm) concentration mode and the
Temperature measurement mode.
Since the mg/L (ppm) concentration value of dissolved oxygen varies with
temperature, barometric pressure and salinity, the meter with its electrode has
to be calibrated with consideration to these factors to ensure a proper
measurement. Therefore, it is very important to set the proper temperature,
barometric pressure and salinity values in the meter prior to any calibration or
measurement process. Since the dissolved oxygen measurements in %
saturation will linearly affect the mg/L (ppm) concentration measurement, it is
important that the meter has to be first calibrated in the % Saturation mode
and temperature mode before commencing the mg/L (ppm) concentration
mode calibration.
In % saturation calibration mode, the dissolved oxygen calibration values will
vary according to the barometric pressure correction set in the meter.
Therefore it is necessary to set the barometric pressure first before proceeding
to % Saturation calibration. The following table is an example which explains
the acceptance calibration values when % Saturation mode calibration is
attempted under different absolute value and under two different barometric
pressures.
% Saturation factory
default value Acceptance Calibration
Value (760mmHg) Acceptance Calibration
Value (760mmHg)
less than 10% 0% 0%
10.1% to 49.9% Err.1 (error 1) Err.1 (error 1)
50% to 200% 100% 92.1%
In the mg/L (ppm) concentration calibration mode, barometric pressure,
salinity and temperature of the calibration sample needs to be set in the meter
prior to calibration. Since the pressure has already been set in the % saturation
calibration which is done earlier and assuming that the calibration is done on
the same barometric pressure and if you are using the temperature sensor in
automatic temperature compensation mode, you only need to input the known
salinity of the calibration sample to the meter. The dissolved oxygen mg/L
(ppm) concentration value can then be calibrated to the known sample
concentration calibration value. Note that the concentration calibration
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