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The technique off my weatherstation
The technique

The station is a La Crosse WS-2357. The console measures indoor temperature, rel. Humidity and air pressure. It is one of the affordable stations with these capabilities. The barometer measures absolute and relative atmospheric pressure. The difference between absolute and relative air pressure must be set, depending on the altitude where the station is located.
1 Hpa is roughly 8 meters from sea level. We are located at 44 meters from sea level. I have adjusted the relative air pressure with a calibrated barometer. Doing that, I discovered a difference between the "real" and the air pressure reading from the La Crosse. All values on this site are relative values and correct.
The outdoor unit, das measure temperature and relative humidity. The device operates in the shade. It can work wireless while running on batteries. Then updates will be send between 32 and 128 seconds to the console. This time period is depending off the measured wind speed. I connected the outdoor unit with a cable to the console. On this way the outdoor unit and the console are power "fed" from main power. The batteries in the console and the outdoor unit are now only used as a backup. Updates on this wired system do happen every 8 sec.
Connected to the outdoor unit are the rain gauge (resolution of 0.25 mm) and wind direction and wind speed meter. The anemometer and the rain gauge are mounted on the roof. The anemometer gave initial problems caused by EMF influence on his 15 meter long cable.
I'll found this solution on the internet. With this modification it works perfectly.
By registering all the data, the chill and the condensation point can be calculated. These are visible at the console. All maximum and minimum values can be made visible on the console.Optionally, various alarms can be set. Example is extreme barometric fluctuations as bad weather announcement and or on the wind speed, as storm warning.
home crafts desk
Top right is a home crafts desk in a bit off colonial style, an old but coddled PC is still perfectly adequate. During the first few months there were a couple off changes made to the various types of software and available computer power I used. 
A brief summary of the past: I'll started with "Heavy Weather" software that generated some picture who where uploaded to this site. Later a second program, "WUHU" was used to upload data to Wunderground. 
Once everything was stable I'll decommissioned "Heavy Weather" and now "WUHU" is used to retrieve the data from the weather station. Via templates "WUHU" uploads every 2 minutes data file's to this site, every few seconds data is locale written in to *.dat file. 
With PHP server scripting I create the different ways of displayed weather data on this site. 
Only graphs are produced local on my computer from these *.dat files with "Graph-Weather" software. These graphs are send, as pictures to this site. 
But it became a bit too much for the old desktop that we also use as a normal computer and internet connection.
Here the outdoor unit located in the shade and conect with a red ftp cable the anemometer on the roof
Now I am running an old laptop with a stripped down Windows XP, 24 hours a day. WUHU is running on this laptop and retrieves the data from the weather station. This happens with a USB to serial cable. WUHU does this every few seconds. Every measurement writes data to a. *.dat file's who are used by Weather Graph. 
Every second minute WUHU is starting a small program written in C. This program reeds out a Analog / digital converter. A homebuilt pyranometer is connected to this converter. This C program writes the measured global radiation value and the time and date of the measurement to a file. It also counts the hours of sunshine. Furthermore, this program ensures the day / night background of the weather pages on this site. 
Weather Graph also uses these file with global radiation data. 
WUHU uploads every 5 minutes data to Wunderground and is using a template to upload every 2 minutes data to this site. Weather Graph provides all graphs (line and bar) and statistics per chosen interval. 24 hours, 48 hours, current month and previous month and upload them to this site.

WUHU "remembers" the high and lows per hour, 24 hours, per day, per month, per year and all time and send them every 30 minutes to this site.There is an automatic backup every day of the critical files to a NAS. Each week the old data files are renamed to week numbers, and a new data files is made fore the current week. Each month a new current and previous month is automatically made for this site. 
The laptop who runs as a Meteohub
When main power fails, (which happens a lot over here), the laptop go's in les then 5 minutes in sleep mode. Every hour the laptop wakes up to see off the main is back. If not, it go's in sleep again. If the main is available, everything will be started and the historical data from the weather station is retrieved. This data is uploaded to Wunderground and used for the information on this site. All this to give a reasonable assurance of continues data. 

he last problem I faced was the date / time of the console. It regularly ran completely out of line. Then the saved data was unusable. The weather station is equipped with a DCF receiver. Normally it means that the clock is neatly synchronizes with a long-wave transmitter in Germany . Unfortunately, we are outside the service area of this station. The long wave receiver of the console was sometimes put on the wrong foot by strange signals. This is weird, because adjustments in a DCF system are only made if the same information repeatedly was received. I have been in consultation with Dick from www.weerspecialist.nl and we decided to dismantle the internal ferrite antenna completely. Now you can presume, reasonably sure, that there is no information received. In order to keep the clock from the console in sync WUHU software now checks every week off the weather station clock is in sync with the PC clock. If the deviation is more than a few seconds, it will be corrected. This works for some time now and without any problems..

Screenshot off the WUHU software