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C A L I B R A T I O N
TEMPERATURE
All cable assemblies have built-in, temperature sensors. Temperature
calibration is not required nor is it available.
BAROMETER
The barometer in the Pro20/Pro20i is calibrated at the factory. The
barometer reading must be accurate to ensure accurate % calibrations
and DO readings. If your barometer requires an adjustment, use the up
or down arrow keys to highlight the barometer box on the run screen,
then press enter
. Next, use the up or down arrow keys to adjust the
barometer reading to the
local, true barometric pressure
. Continually
depress the up or down arrow keys to change the barometer value more
rapidly. Press enter to confirm and save the barometer adjustment.
Do not use a barometer value that is corrected to sea level.
Laboratory barometer readings are usually “true” (uncorrected)
values of air pressure and can be used “as is” for barometer
calibration. Weather service readings are usually not “true”, i.e.,
they are corrected to sea level, and therefore cannot be used
until they are “uncorrected”. An approximate formula for this
“uncorrection” is:
True BP = [Corrected BP] – [2.5 * (Local Altitude in ft above sea level/100)]
Although the barometer range is 400.0 to 999.9 mmHg, you will be
unable to adjust the value across the entire range. The barometer is
very accurate and the instrument will not allow you to adjust the value
drastically beyond what it is measuring during calibration.
DISSOLVED OXYGEN
The Pro20/Pro20i can be easily calibrated with the press of one key by
enabling One Touch Cal in the System Setup menu and following the
One Touch Calibration procedure.
Ensure the barometer is reading accurately before performing a One
Touch Calibration, DO %, or DO Local% calibration. These calibration
procedures use the barometer reading during calibration. If the
barometer reading is erroneous during a calibration, your dissolved
oxygen values will be inaccurate.
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