Basic Weather Station BWS-200
A-4
A.5 Modifying the Program
A copy of the standard program (BWS200.scw) is supplied to you on disk with
your BWS-200 for your convenience. It has been written using a program called
SCWIN (ShortCut for Windows) which is a module of the PC200W accessible
from the “Short cut” button in the top right hand corner of you r PC200W screen.
To edit it please copy the BWS200.scw file to C:\Campbellsci\PC200W on your
hard drive, open PC200W, click on the “Short Cut” Editor button and open the
file from there. A separate file with a .CR2 ending will be generated. This should
be loaded onto the datalogger. Please note that programs cannot be retrieved from
the datalogger so a copy should be kept secure at all times.
Short Cut automatically allocates the wiring on a first come first
served basis. Since your datalogger has come pre-wired it is
important that, if you generate a new program from scratch, or edit
the standard program, that you add the sensors in a consistent
manner with a view to maintaining the original wiring associated
with the Standard program. The order in which the sensors have
been added is as follows:
CS215
03002-5 (CSL)
ARG100 (CSL)
CS300
CS100
A.6 Calculating ETo
To calculate Evapotransporation The Penman-Monteith calculation method is
used. ETo is calculated on an hourly and daily basis. The daily ETo is reset at
0100 hours each day.
Because the calculation relies on meteorological data, the sensors for air
temperature, relative humidity, wind speed and solar radiation must all be present
and recorded before ETo can be calculated . Solar radiation, measured wit h the
CS300 is an optional extra sensor.
The ETo Calculation additionally relies on the following site specific data:
Site Latitude
Site Longitude
Site Elevation
By default your Weather Station is programmed to assume a mid European
latitude of 50 degrees north on the Greenwich Meridian (ie Longitude 0 degrees
E) at sea level. For most purposes this assumption is perfectly adequate. However
you can customise these values should you wish to.
To do so open the program in ShortCut. Click on the Outputs menu item on the
left hand side, click on the “ETo” field in the “Processing” column on the left
hand window of the screen and click on the “Edit” button at the bottom. A
dialogue box will open up and the values can be altered to suit, saved as a new
program and downloaded to the logger.
NOTE
