The Nailsworth Weather Station

Weather Station The photograph shows the weather station measuring equipment on the roof of NailsworthWeather.

The weather station was set up in November 2001 and was based on the Oregon Scientific WM918.

That was replaced after long service in May 2010 with a Davis Vantage Pro station. The photographs show the old setup as I have not yet got around to updating them although nothing changed much other than the equipment.

Stevenson Screen
Rain Collector
WM918 Console
Old WeatherVane

The top photograph shows the main wind collecting instruments. The funny shaped aerial above the satellite dish is a NOAA 137MHz weather satellite receiver aerial. Due to my location this only seems to be able to receive data from NOAA 17. The software looks like it cant be left to run in automatic mode, so this has been shelved until I get some spare time to look into it.

As you can probably tell from the photograph, Nailsworth is in a valley, but my location provides reasonably clear wind runs from most directions except perhaps the strongest westerlies. The top photograph was taken on a 1st November 03 as the weather and lighting seemed extra special.

The second picture shows the radiation shield that houses the thermometer. Actually it houses two thermometers as I am also running a wireles station (WMR928N) alongside the old one. I'm doing this as I wrote the software that collects the data from the WM918 unit and thought that I may as well make it work with the wireless unit as well. The white rain collector is part of the wireless station setup and is not connected to the website as its not in the best location for collecting rain what with it being sheltered behind a satellite dish. Due to my loction there arnt many places to bolt things to!

The rain collector is a small black bucket that has a small sea-saw thing inside it. Basically, the rain fills up a small bucket at one end, this tips it and in doing so it passes a small magnet controlled switch (a reed switch) which sends a pulse to the weather station. The other end then fills up with rain and the thing tips back. Each sea-saw action requires 1mm or rain, therefore giving the unit a 1mm resolution. The unit is fully automatic in operation.

Although the unit comes with some computer software, as is normal it only half works unless you get the old credit card out and register it. As I write software for a hobby, I decided to write my own, thus giving me all the options that I required and the easy ability to add anything new as and when I wanted.

I have made the software available here as a free download

I prefer analogue dials to digital readouts, so the software displays both digital and analogue. The dial needles are damped in software, which makes them look more realistic.

The finished result, one of the screens is shown in the photograph. The screen displays all the information that can be easily read from a distance. Other options display graphs and Maximim and Minimum recordings. Data is stored in a .csv file and is written to it every couple of minutes. Each month has a seperate file, so you can easily find the data you want.

The weather station as supplied is not the the most robust design electrically speaking as the wires to the wind and rain sensors are in effect huge long aerials. These can (and do) pick up electrical interferance and will cause the weather station to report that it's raining like it's never rained before, and or blowing a hurricane when it's actually a calm day. Not good!

To combat this I replaced the cables to the anenometer and rain bucket with good quality screened cable which fixed most of the problems. A well known modification using opto couplers is documented on the Internet, but this involves taking the weather station apart and soldering these devices onto the main board. This is not very practical if you don't want to void the warrenty and you can't solder. As I do electronics for a living I thought it would be better to have the additional electronics in a separate box. If it's placed close enough to the console it should work just as well as the other mod. Needless to say I have produced some small PCB's and and fitted them into a small container. This is available on the WM918 fixes page on this website.

The second from last photograph shows an earlier weather station based on a kit from Maplin Electronics. This was hooked up to a 286 (remember those) that ran DOS. It was nothing special, but it worked for a year or so. The main problem was that the bearings in the anemometer would sieze after about a year. After I got through two anemometers they stopped making them so I gave up! This was circa 1993.