A pair of Davis GroWeather (see ``http://www.davisnet.com'') weather stations acquired from a local systems integrator, Envia Oy, have performed satisfactorily. The more completely equipped ``upper'' weather station is depicted in Figure 16.
Both GroWeather stations feature temperature, barometric pressure, and relative humidity sensors. The first station is located near the telescope and radome, and the second one is a bit farther away and about 10 meters lower in altitude. It acts both as a backup of the first station, as a ``second opinion'', and also hopefully as an ``early warning'' system, as mist and dew seem to appear first in the low-altitude ``valley'' area. The ``hi'' station includes additional solar radiation, wind speed and direction, and rain gauge sensors which were omitted in the ``lo'' station.
Isolated RS232/RS422 converters were designed in-house to provide a reliable way to connect stations to meacon Linux computer. RS232 is not reliable with long cable runs (50/180m in this case) whereas RS422 works reliably up to 1000m and more of twisted-pair cable. Our converter combines complete electrical isolation (including power supply and ground) together with standard RS422 drivers with surge suppression, thus forming a robust interface for outdoor cabling.
Weather station data collection software ``weatherd'' was put into full use after completion and installation of the isolated RS232/RS422 interface adapters. Software saves all data from stations in two different locations ``/data/weather/hi'' and ``/data/weather/lo'' based on the physical location of stations. The ``MB'' software presented in section 2.1.9 makes it easy to generate customized weather plots using a Web-based end-user interface.
