YSI Pro20 - Manual (Page 21)

EXITING THE SYSTEM SETUP MENU
To exit the System Setup menu, press the down arrow key until the ESC - Exit box
is highlighted, then press enter to return to the run screen.
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 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:
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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.
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