Categorie archieven: Techniek

RPi weather station: the construction

The original material used by Alecto was plastic and light-weight aluminium tubing of 20 mm diameter. Because I needed to mount both a wind velocity meter and a wind direction sensor, I needed some more material and I decided for the robust zinc-coated iron tubing as used for central heating systems. These come in 22 and 15 mm diameter versions with actually quite elegantly looking junctions. I chose for the main pole of the thicker diameter tubing with a parallel side branch of the thinner tubing. With this construction, I could also mount the rain gauge and the Stevenson screen which held the rest of the measurement system: temperature, pressure, humidity and solar radiation.

IMG_7710

The rain gauge is of the self-emptying tipping bucket type. Here the bucket is assumed to be measuring 0.3 mm rain per bucket. Every time a bucket is full, it empties  and causes one momentary reed contact closure which can be recorded by subsequent equipment. The Alecto way of mounting the rain gauge is by a single plastic bar. That makes it extremely sensitive to vibrations, it almost does so by itself!  Vibrations would make the inside balance wiggle and cause erroneous contact closures; a known problem of these devices. Therefore, two extra bars are attached to the central rod as shown below.

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