This is a breakout board for feeding the rain bucket and solar sensor signal into the cabling at any point between the base station and the wind tree. The USB connector is to power the system if it is more convenient to feed the power somewhere along the path to the wind tree as opposed to feeding it directly to the base .
The circular board is the distribution board for the wind tree. It brings out the connections for Wind-speed, Wind-Direction and Solar and is housed in the bottom of the wind tree.
A complete station without a aspiration fan consumes 7/8 of a Watt .