Instruction Manual
9
*Table 3 Subroutines
End Program
-Input Locations-
1 P_mb
* Proper entries will vary with program and datalogger channel, and input location assignments.
5.4 Output Resolution
When storing the values from the CS100 to a data table or to a datalogger’s
final storage location, care must be taken to choose suitable scaling of the
reading, or to store the value with adequate resolution to avoid losing useful
resolution of the pressure measurement. The default resolution (low
resolution) for Campbell Scientific dataloggers is limited to a maximum of
four digits. Even then, the maximum digit value that can be displayed is
6999 for Edlog dataloggers, and 7999 for the CRBasic dataloggers. If you
use this option with barometric data scaled in millibars (hPa), a reading
above 799.9 mb for CRBasic dataloggers or 699.9 mb for Edlog dataloggers
will lose one digit of resolution, e.g. at 900 mb, the resolution is limited to
1 mb.
To retain 0.01 mb resolution, you either need to deduct a fixed offset from
the reading before it is stored to avoid exceeding the 799.9 for CRBasic
dataloggers or 699.9 for Edlog dataloggers threshold, or output the
barometric reading in high resolution format. This can be done by using the
IEEE4 format for the CR800, CR850, CR1000, CR3000, CR5000, and
CR9000(X) dataloggers or using the Resolution (P78) instruction for our
Edlog dataloggers. The default data output format for CR200 series
datalogger is IEEE4.
6. Correcting Pressure to Sea Level
The weather service, most airports, radio stations, and television stations
reduce the atmospheric pressure to a common reference (sea level).
Equation 1 can be used to find the difference in pressure between the sea
level and the site. That value (dP) is then added to the offset (600 mb in our
example programs) in the measurement instruction. U. S. Standard
Atmosphere and dry air were assumed when Equation 1 was derived
(Wallace, J. M. and P. V. Hobbes, 1977: Atmospheric Science: An
Introductory Survey, Academic Press,
pp. 59-61).
dP
E
=−−
⎛
⎝
⎜
⎞
⎠
⎟
⎨
⎪
⎩
⎪
⎫
⎬
⎪
⎭
⎪
1013 25 1 1
44307 69231
5.25328
.
.
(1)
The value dP is in millibars and the site elevation, E, is in metres. Add dP
value to the offset in the measurement instruction.
Use Equation (2) to convert feet to metres.
(8 pages)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Comments to this Manuals