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Barometer
The ProSwap and ProDSS handhelds have a built-in barometer. The barometer is factory calibrated and should rarely need to be
recalibrated. The barometer is used for DO calibration and for virtual vented depth measurements. Verify that the barometer is
accurately reading “true” barometric pressure and recalibrate as necessary.
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 cannot be used until they are
“uncorrected”. Use this approximate formula:
True BP in mmHg=[Corrected BP in mmHg] - [2.5* (Local altitude in ft. above sea level/100)]
Example:
Corrected BP = 759 mmHg
Local altitude above sea level = 978 ft
True BP = 759 mmHg - [2.5*(978ft/100)] = 734.55 mmHg
Barometer Calibration
1.
Push the
Cal
key, then select
Barometer
.
2.
Select
Calibration value
then enter the correct “true” barometric pres-
sure.
NOTE:
The measurement units during calibration are dictated by what is
enabled in the sensor setup menu. Be sure to enter in the correct
units.
• BP in mmHg=25.4 x BP inHg
• BP in mmHg=0.750062 x BP mb
• BP in mmHg=51.7149 x BP psi
• BP in mmHg=7.50062 x BP kPa
• BP in mmHg=760 x BP atm
3.
Select
Accept Calibration
. “Calibration successful!” will be displayed in
the message area.
Sensors, Calibration, and Maintenance
4.11