My Hobby-Boards solar sensor went "live" on 14/2/09, when it was placed in full view of the sky at the bottom of the garden.
This graph shows the amount of light energy (measured in "W/m2", watts per square metre) over time... basically how sunny its been!!
Dips in the graph show when clouds pass.
Todays solar levels:
Heres some examples of sunny and cloudy days.
This was a very sunny day with unbroken blue skies. The sudden drop at about 17:00 is when the sun goes behind a neighbours tree.(The "saw-tooth" effect on this graph is a "feature" of the software, and not even the Programmer is sure why..!!)Here is dull day...what a difference a couple of days makes..! Sunshine Hours
Once the light level reaches a certain level, determined by calibration on sunny days, the system will record how many hours of sunshine we've had.
Evapotranspiration is the estimated amount of water that evaporated from the ground and plants, and is calculated on temperature, solar radiation, humidity, and wind speed.
The solar sensor is a "Photodiode" which produces a very small electrical voltage, (measured in milivolts, 1mv = 1/1000th of a volt), when light reaches it, and the more light, the higher the voltage. This voltage is picked up by Weather Display which calculates the Watts of energy per square meter (W/m2)
Weather display also calculates the predicted maximum W/m2 value for the time, date and location of the weather station, and then calculates the current percentage of maximum. (Both the raw voltage, and the percentage of estimated maximum W/m2 are shown at the top of the ET graph)