SonTek/YSI
ADVField/Hydra Operation Manual (September 1, 2001) 75
Pressure_dBar = Pressure_Offset + (Pressure_Scale * Pressure_Counts)
where
Pressure_dBar = measured pressure in dBar
Pressure_Offset = offset calibration constant set at factory
Pressure_Scale = scaling calibration constant set a factory
Pressure_Counts = measured pressure in counts as output over the serial port and stored in
the binary data files
The values for Pressure_Offset and Pressure_Scale can be accessed three ways: through the di-
rect command interface (using
PressScale
and
PressOffset
; see §3.9), from the data conver-
sion software
*.CTL
file (see ADVField Software Manual), or directly from the binary data file.
In the first two methods, the constants are output with units of (dBar) and (dBar/count) respec-
tively and can be used directly in the formula above. When using the binary data directly: Pres-
sure_Offset is stored in units of µBar and must be multiplied by 10
5
; Pressure_Scale is stored in
units of (nanoBar/count) and must be multiplied by 10
8
before using in the above equation.
When using the data conversion software to extract ADV binary data files into ASCII format, the
software automatically does the conversion from counts to dBar (see ADVField Software Man-
ual).
Note that since the pressure sensor is located in the end cap of the conditioning module, it will
not necessarily be at the same depth as the sampling volume. The difference will depend on the
probe configuration and the orientation of the probe. Be sure to consider this when processing
combined velocity and pressure data.
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