May 6, 2004 My Weather Site Information Hardware and Software Overview The weather information on this site is collected by an Oregon Scientific WMR-968. This unit has wireless sensors, a touch panel display and includes a serial port for interfacing with a computer. Each of the sensors is powered by batteries and recharged via solar panels. For my review of this unit click here. The sensors include an outdoor temperature/humidity sensor, an anemometer (wind speed and direction gauge), an indoor temperature sensor/barometer, and a rain gauge. There are two programs I use to generate the html pages for this website. The first is Ambient Software's Virtual Weather Station. This program reads the WMR-968 data through the serial port, logs the data, and creates images and the web pages containing weather information at specified intervals. It also sends data to the Weather Underground for my station. The other program I use for the weather forecast is a program I wrote called Bucket O' Brains Weather Parser. This program generates an HTML webpage forecast from a National Weather Service HTML forecast. I have another program that I wrote that retrieves the National Weather Service daily temperature records from a daily climate text file they generate. The outdoor webcam image is generated by ImageSalsa. Imagesalsa can import data exported from Virtual Weather Station and add that information to images. Tips for Setting up a Weather Station The following are some setup considerations for the WMR-968 units. First, you must setup the anemometer to point to true north; not magnetic north. This means you have to have a compass, and know the magnetic declination of your location. Here is a site explaining all that in detail. I recommend not setting your anemometer on your roof if at all possible. I have tried setting mine on my roof on a 4' mast and on a ground mast about 18' high and have had much more accurate readings on the ground mast. Unless you can raise your anemometer high enough off your rooftop I believe that the winds are affected both in direction and speed by the rooftop itself. Another tip for the anemometer if you live in a climate where there is freezing weather is to have some way to easily access the sensor itself. Unfortunately the WMR-968 anemometer can be made inoperative in freezing rain conditions, and the only way to get it working again is to manually (and carefully) remove the ice from the unit. Putting the unit on the roof can make this a dangerous proposition in wintery climates. NOTE: Ensure that any mast you mount the anemometer to is grounded, as it can build up a static charge that can cause the unit to become inoperative. There is a grounding strap for the anemometer - make sure it is connected to the grounded mast! It is also important to not place the outdoor temperature/humidity sensor in direct sunlight, as this can heat up the sensor and give erroneous readings. Make sure you either place the unit in the shade (I originally mounted mine under the house eaves in the shade) or in a radiation shield. Here are some commercial examples of radiation shields: 1 2 3 Finally, the rain gauge must be mounted so that it is as level as possible, so the tipping bucket works properly. Here is a handy forum that discusses WMR-918/968 setup issues.
Sensor Mast: The outdoor sensors are mounted on a wooden 4x4 post buried in the ground. The anemometer is on an 18' metal pole made from two sections of 1 1/4" electrical conduit welded together. This metal mast is mounted with conduit straps and screws to the wooden pole, and can be taken down to clean the anemometer in the event it gets frozen. Solar Radiation Shield: I constructed an active solar radiation shield from 10 white plastic cereal bowls, 1/4" threaded steel rods, nuts, plastic spacers, and some rigid foam insulation. The fan inside the shield is a miniature 12VDC fan from a computer CPU cooler, and is powered by a 12V solar panel salvaged from a broken solar electric fence controller.
I cut a 3 1/4" hole with a hole saw in the bottom center of each bowl except for the two that would be mounted at the top. I also drilled 3 @ 1/4" holes in each bowl for the rods. I made 1" plastic spacers from 1/2" ID poly tubing cut on the bandsaw. The shield was assembled with two bowls at the top without center holes, the topmost having a circle of 1/4" thick rigid foam glued to its underside (for extra insulation). The plastic spacers were then placed on the rods to space the bowls apart. On top of the cutout of the fifth bowl I placed the fan, that is positioned to draw air up from the bottom of the shield and blow it out the top. The fan draws its power from the solar panel mounted above the radiation shield and thereby only runs during the daylight hours.
I made a plastic bracket with two holes that mounts on two of the metal rods to attach the temperature sensor to, which was attached to it with a nylon zip tie.
It was mounted about midway down from the top of the unit. The red and white modular plug is the power cable for the fan, which attaches to the solar panel.
The entire shield unit is mounted to the post by a angle iron bracket that is bolted to two of the mounting rods. Rain Gauge Mount: The rain gauge is mounted on a 1 1/4" rigid PVC conduit 90 degree elbow attached to the wooden pole with metal conduit straps. It sits on an acrylic base attached to the elbow with three leveling bolts.
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