I use GNUPLOT to do the plotting, a complicated perl script to extract the data from a Mysql database. The useful thing about GNUPLOT is that it does time series data well. It also auto scales and everything. However, it is getting long in the tooth and has some bugs with time scales -- in particular if you look at a graph generated during the day for the current day, then often some of the hour ticks are missing. Maybe I ought to check to see if there is an updated version. Ahah -- there is, and this problem has been addressed. Now installed.
That uses perl and libplot. All the lines are drawn by the perl code to make it look pretty.
Each sensor, and there are around 10, gets an entry in the database every 5 minutes. The actual data being logged depends on the sensor, but mostly it consists of min/max/avg for the 5 minute period. The software polls the sensors as fast as it can, so I get 20 or more readings per sensor in each 5 minute period.
That is a tricky question. It depends if you want to do it on the cheap (like me), or really want something turnkey. If you want to build it yourself, then the iButton website is a cool place to start. Also check out the archives of the weather mail-list. There are a number of commercial weather station products -- some of which may be cheaper than doing it yourself.
In principle, yes. The bad news is that it is all rather jury-rigged together. It works for me, but it probably won't for you. I'm not averse to giving out stuff, but do not expect a turnkey solution for anything!