The weather station used is a Lacrosse Technology WS2003. It consists of an indoor base unit and 3 outdoor sensor units. The base unit can connect to the external sensors either by a wired or wireless link. I have used a wired link as it has a faster refresh rate and enables the sensors to be powered by the base unit. The base unit and the outside temperature module also have a battery backup in case of power failure. The windvane and rain sensor are powered from the temperature module.

Base Unit

The Base unit receives and displays the readings sent by the outside temperature, humidity, wind and rain units. With a wired connection this happens every 8 seconds. If I was using the 433Mhz wireless connection the fastest update would be 32 seconds and could be as long as 128 seconds, depending on the wind speed. The Base unit also records the indoor temperature and humidity. Although readings are received and displayed every 8 seconds they are not stored in memory this often. The base unit can only store up to 175 data sets before old data is overwritten. As my PC is only on during the day I decided to set the recording interval to 10 minutes. This allows the unit to store at least 29 hours of data before it needs to be downloaded to my PC, so if I go out for the day I know I won't lose any data. If I am away for the weekend I change it to every 15 minutes and that gives me 43 hours before data is lost. This is the feature I am least happy with as it means the wind speed measurement is not very good at recording short gusts. Firstly, if the gust lasts less than 8 seconds it can be missed completely and secondly, if the gust is read by the base unit but it does not happen at the same time as data is being saved it is not recorded in the data. The only way to get more accurate data is to reduce the recording interval, say to every 15 seconds, but that reduces the base units 'stand alone' time to less than 45 minutes, so my PC would need to be on 24/7, and the number of saved readings would rocket to 5760 per day, or approx 178000 per month.

Timekeeping for the base unit is controlled by receiving a radio time signal from a transmitter in Braunschweig Germany rather than the UK time signal transmitted from Rugby. If the signal cannot be received you can set the time manually. I have had no trouble receiving the signal in west Wales. It is necessary to set the correct time difference between the UK and Germany manually. The base unit allows the setting of alarm values for all readings and for a storm warning. As well as displaying the data from the sensors it calculates and displays dew point and wind chill values and stores max and min values since last reset. It also measures and displays relative and absolute pressure and rainfall over the last 1 hour and 24 hours. Connection to a PC is via a supplied serial cable which requires a 9 pin d-type connector on the PC. Data is automatically downloaded from the base unit to the PC using the supplied Heavy Weather software.

Wind vane & anemometer

The wind vane registers one of 16 possible compass directions and is free to rotate through 360 degrees. The anemometer is a 6 blade ducted fan rather than the conventional cup style and is on the same axle as the windvane so is pointed into wind by the vanes weathercocking action. The unit is connected via a 4 way telephone style cable to the temperature module. This cable provides power to the windvane from the temperature module and allows data transmission from the windvane back to the temperature module. The windvane unit cannot work wirelessly.

The windvane is mounted on a 3 metre pole fixed to the side of my garage roof. Overall it is about 16ft high. This is insufficient to get it above the turbulent air created by surrounding objects. We are also surrounded by mountains which funnel the wind into different directions from the general flow so readings can only be taken as a guide to the general direction. So far, despite severe wobbling, it as survived the welsh weather. The highest recorded gust so far has been 68.2mph

New Wind vane & anemometer

In July 2008 the original windvane stopped working. It had been playing up for some time, particularly when it was raining. I had taken it down a couple of times and dismantled it, but had never actually found it damp inside. Finally it gave up completly so I ordered a replacement from the Weathershop in Porthsmouth. I had a choice of buying an identical replacement with the ducted fan type anemometer or one with a more traditional cup type anemometer. I opted for the one with cups. This was partly because I felt that the ducted fan unit was slower to react to gusts as it had to be turned into wind by the vane before it would get the full fource. In turbulent conditions I felt this delay, although small, was reducing the gust readings. Only time will tell.

I have left the original cable connected to the new windvane. I had replaced the cable on the original windvane because it was picking up interference and generating false readings. I will have to do the same again if it proves to be a problem with the new unit.

Rain sensor

The rain sensor consists of a funnel that collects the water and directs it to a pair of buckets arranged like scales. As one bucket fills it tips over the scales allowing the second bucket to fill before it tips back again. Each tip is registered by a magnet activated reed switch. Each tip corresponds to 0.518mm or 1/200th of an inch of rain. The unit is connected via a 4 way telephone style cable to the temperature module. This cable provides power to the rain sensor from the temperature module and allows data transmission from the rain sensor back to the temperature module. The rain sensor cannot work wirelessly.Readings are relayed to the base unit about every 2 minutes.

Temperature and humidity sensor

The temperature and humidity module measures the outside temperature and humidity of the surrounding air. It's placement is critical to accurate recording. It must not see any direct sunlight but must also have free air movement around it. The module acts as the hub for the other sensors and is the only unit that connects to the base unit. This can be with a 4 way telephone type cable or wirelessly.

Computer

Initially, the weather station was linked to my 'everyday, desktop computer. This is a 2.8Ghz P4 running Windows XP. Amazingly, the Heavy Weather software consumes nearly 30% of the CPU's resources when running. The PC uses about 100W of electricity when in 'standby' mode, i.e. with the monitor off and the drives stopped. I had a hunt around for a cheap laptop to dedicate to the weatherstation and found a Dell Latitude CPi going cheap. This only has a 400Mhz PII processor, 128Mb of memory and a 6Gb hard disk running XP. It takes a full 5 minutes to boot up and load all the software, but once running copes with Heavy Weather and Dorgem (webcam software) OK. It only consumes 9-10Watts and has the advantage of battery backup in case of power cuts, which are not uncommon up here. I am thinking of leaving it on all the time, but currently turn it off at night, just to be safe.