The author is a retired mechanical engineer who enjoys his 2nd home at the Lake, both winter and summer, and probably splits time about 50/50.
By: joecook1 , 5:56 AM GMT on February 16, 2007
This entry is to describe the Why and What of our recently installed weather station.
We decided to do our own Personal Weather Station (PWS) because there was a total absence of PWS data in our area and the existing data from Chester and the PG&E at Prattville (CEDC on the web) was delayed, sometimes missing and subject to questionable accuracy at times. It seems that whenever there is a major storm, the CEDC server gets overloaded and drops out for hours/days at a time. As a snowmobiler with a place in Chico also, we wanted the capability to know when it was snowing/raining, how much and maybe have a visual via a webcam of what was going on at Lake Almanor. With the Wunderground PWS network and the software available in addition to the quality weather stations, it was an easy decision to do the deed.
After checking the usage of various PWS units and their specifications we narrowed it down to the Oregon Scientific WMR698 and the Davis Instruments Vantage Pro2. The edge in the specs went to the Davis with regards to accuracy and resolution. Then we checked the user comments of both and it looked like the Davis had the higher quality and fewer problems. So we got the Davis VP2 with WeatherLink (Internet), the rain collector heater since we normally have snow in the winter, and the mounting pole. After checking pricing at various locations, we purchased it from Ambient Weather. Link We got the model 6152C cabled unit with standard radiation shield since our chosen mounting location was close to the cabin.
BTW, the rain collector heater was another plus for the Davis since the OS guys either don't recognize the need or choose to ignore it. Having now installed it, I can see that it is pretty generic and could be installed in most rain collectors without much extra work.
The unit came via UPS ground in a very timely manner. I was equally impress with the packaging of the Davis. It arrived without the usual UPS corner bashing, but the equipment was so well packaged and protected that I think it would have withstood considerable mishandling.
The assembly instructions were detailed and accurate (and well written by someone familiar with tech writing). The assembly (there wasn't a whole lot required) was straight forward and the parts fit as designed, like the anemometer drip shield and the cup assembly.
The unit comes with the sensors of what they call the Integrated Sensor Suite (ISS) pre-wired to the interface module. The remainder of the hook up at the ISS requires opening the interface module cover and pluging in the connector from the anemometer ("Wind") and the 100' console cable ("Console"). This requires feeding the RJ14 connectors thru a small hole in the bottom. After the "Wind" connector had been put thru and connected, the remaining space in the feed-thru hole was pretty limited and the it took some finesse to finally get the Console connector thru. But it was accomplished without damage to anything. I have to think that if you also had the solar and UV sensors to feed thru that same hole, it would present a bigger problem.
The rain collector heater was installed under the rain collector (which is easily removed by rotating about 10 deg.) before the ISS was installed on the pole. This amounted to putting 2 self tapping screws in place, then attaching the heater power cable, which had been fed thru a hole in the bottom of the unit, with two terminal screws. The power cable is a 4 wire shielded unit that requires striping the wires and twisting the two black wires together and twising the red and white wires together, thus making a 2 wire cable with double the rating.
The Console cable and the heater power cable were routed inside the cabin where the Console cable plugs into the console with no further preparation. The heater power cable is then cut to length to correspond to where you want to control the heater. The power supply consists of a transformer/rectifier unit, which provides 24 vdc, and a switch unit that also contains a fuse. After stripping and twisting the power cable wires, same as ISS end, it is fed thru a hole in the switch unit and connected to the terminal block. A tiewrap is applied inside to provide strain relief. The switch unit switch is labeled "On" and "Off" and provides a green LED that is lit when the unit is "On".
The "Console" provides a display of the sensor values (Temperature (inside and out), Barometric Pressure, Humidity (inside and outside), Heat Index, Wind speed and direction, time and date, as well as some calculated values like Dew Point, Wind chill, et al, available with selection buttons. The console requires 3 C cell batteries to be installed for backup in case of power failure. The console has its own power supply unit that plugs into 110 vac and has about a 6' cable that plugs in the bottom of the unit. My setup uses the USB serial port and there is a USB cable that is supplied with the unit that goes from the console to the PC computer. In order to use this cable, it is necessary to install the Data Logger (DL) module. This is easily accomplished with the removal of a pop off cover on the back (same one removed to install the batteries). The DL plugs directly into a connector (about 19 pins) and has a short 4" pigtail connector for the USB.
And that completed the physical installation process.
We'll talk about the software in a subsequent entry.
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