12-02-2017, 19:28
Hi,
The difference in the amplitude of the two "spikes" in the afternoon are noteable. It's probably a "sampling" issue: generally Cumulus (and other software) just takes a "snapshot" reading at a particular instant after each logging interval. That makes comparison very difficult for values that are changing from minute to minute, or even second to second. Of course Cumulus can maintain a running average for wind speed, but not AFAIK for the Solar measurements.
For Solar calibration you really need a cloudless sky, not just a clear view of the sun, because light can be reflected off clouds and increase the apparent insolation. So Calibration is a lot easier for those in Portugal or Australia than here in UK.
700 W/m2 seems too high for your location at this time of the year, if the sensor is horizontal. The Cumulus "(Theoretical) Solar Max Rad" curve (select a graph) should give a fair indication during most of the day (I have some doubts about the level near sunrise/sunset at our latitudes).
Cheers, Alan.
The difference in the amplitude of the two "spikes" in the afternoon are noteable. It's probably a "sampling" issue: generally Cumulus (and other software) just takes a "snapshot" reading at a particular instant after each logging interval. That makes comparison very difficult for values that are changing from minute to minute, or even second to second. Of course Cumulus can maintain a running average for wind speed, but not AFAIK for the Solar measurements.
For Solar calibration you really need a cloudless sky, not just a clear view of the sun, because light can be reflected off clouds and increase the apparent insolation. So Calibration is a lot easier for those in Portugal or Australia than here in UK.
700 W/m2 seems too high for your location at this time of the year, if the sensor is horizontal. The Cumulus "(Theoretical) Solar Max Rad" curve (select a graph) should give a fair indication during most of the day (I have some doubts about the level near sunrise/sunset at our latitudes).
Cheers, Alan.