My New Weather Station – Part Two
In my last post I described the first steps in setting up my new Oregon Scientific WMR88 weather station: installing the base station to get indoor temperature, humidity readings and atmospheric pressure readings. In this post I will go into the process I undertook to install the outdoor sensors.
The WMR88 comes with three outdoor sensors:
- Temperature & Humidity
- Wind Sensor (Anemometer & Wind Vane)
- Rain Gauge
(Some special offers from Oregon Scientific also supply a UV sensor with the WMR88. Not mine however, but as I live in Scotland I don’t think that I need fear over-exposure to UV. The base station also supports up to three Temperature & Humidity sensors. I am currently considering purchasing another such sensor which I can move around my house).
I describe the installation process for each sensor below. Even with the supplied fit kits each required a little DIY on my part. DIY is something I enjoy but not something I am very good at. I therefore limit myself to small jobs where I cannot do too much damage and hire professionals for the big jobs. Fortunately the sensor installs were all relatively simple.
Temperature & Humidity Sensor Install
The Temperature & Humidity sensor is a very small unit which comes supplied with a plastic wall bracket with two fixing points. It doesn’t come supplied with fitting screws like the other sensors so I raided my loose screws box for those. The sensor needs to be placed around 1.5m from the ground and be shielded from direct sunlight and rain. More expensive weather stations come with a shielding box for this type of sensor. I would have to improvise.
I picked a spot on my fence that doesn’t get much sunlight and is partially shielded from rain by a fence beam. Fitting the sensor in place was simple enough using the wall bracket but the sensor was still a little too exposed to the elements for my liking. Fortunately I had some planks of wood-effect plastic left over from a recent door and window fitting I had at my home. I cut several pieces to size with a saw and fashioned a small shelter to shield the sensor from rain from above and sunlight from the front. This arrangement protects the sensor but leaves it well ventilated.
Here the finished product viewed from above:
The only calibration required is to switch the sensor to channel one via a small switch inside the battery compartment. Channel one is reserved by the base station for external temperature and humidity readings.
Wind Sensor Install
Next was the wind sensor. Ideally this should have been placed high up above the roof of my house. I don’t like heights much and wanted the sensor to be accessible – after all it is battery powered and the thought of hiking up a ladder to replace batteries frequently fills me with dread. I was prepared to sacrifice the quality of readings for convenience by placing the sensor lower down. Where I live the prevailing wind direction is from the west. Happily there is a good spot near one of the side gates to take advantage of this. This happens to be right beside the Temperature & Humidity sensor.
Again, more expensive kits will come with a mounting pole, but not the WMR88. I got my pole from an old broom, painted it the same colour as the gate and drilled five fixing points through it and into the gate post. Attaching the pole to gate post with screws gave me a sensor height of eight feet. The supplied connector and U-bolt can be attached to any reasonably thick pole and the wind sensor slots easily into the connector.
The only tricky part was ensuring that the wind sensor was pointing North. With a round pole and the U-bolt it is easy to adjust the wind sensors facing before a final tightening to keep it in place. I used my iPhone’s built in compass to ensure I had the sensor facing North.
Here is the finished installation:
Rain Gauge Install
The rain gauge was the most difficult sensor to install. It has to be in an open area and must be completely level. The former ensures that the funnel captures the required amount of rainfall for an accurate reading while the latter helps captured rainfall to drain away easily. My shed (only a few meters from the other sensors) is a good spot for capturing rainfall but has no flat surface. To get around this I built a small shelf onto the side of the shed just under the roof line using a couple of steel brackets and some spare wood. The wood was not completely flat but the fit kit comes with a number of washers that solved this issue. Using a spirit measure and the supplied washers I was able to secure the rain gauge to its shelf by each of its four screw-mounted feet such that it was completely level.
The finished product:
With all three sensors in place and the supplied batteries inserted into each I retired inside to check that I was receiving data on the base station. It was soon raining and the wind was increasing nicely (did I mention I live in Scotland?). This was fortunate as I could confirm readings from all of the sensors and see them alter in response to the changing conditions.
At the time of writing I have had my weather station operational for a week. It is quite interesting to compare what the weather station tells me as compared to what I can see out of the window. I have noticed that previously I had a tendency to over-estimate what I was seeing outside. For example, when I think it must be very windy the weather station actually tells me that the conditions I am seeing are only the result of a 20 mph moderate breeze as opposed to the strong wind I presumed was present. The same goes for rainfall – while a sudden downpour may look to me like it is dumping an inch of water the rain gauge reports a more reasonable couple of millimetres.
In my next post I will conclude this series by investigating using a PC to extend my weather station for data logging and publishing weather data to the web.