Vantage Pro2 sun sensor archived data

[Onepk]

Hi,  Not sure why Google took so long, but I've only just come across this forum after quite a while of searching.  Compared to other sites I've tried there also seems to be a fair number of pundits around so I'm hopeful I might get further with my queries this time!

I acquired a VP2 kit a few months back and have had some questions about the sun sensor ever since, but I'll start with just a couple of simple ones to do with the archived sun sensor data (WeatherLink).  The documentation says that for the temperature sensor (with archive intervals <= 10 mins) the samples are taken every 5 secs and averaged over the required archive interval.  It also says the sun sensor data are averaged (if averaging is selected), but as far as I can see gives no further details about sampling rate.

I am using an archive interval of 1 minute and was intrigued by the archived sun sensor data when compared to the console values.  The latter are described as the "current value" in the documentation and can indeed be seen to change in a matter of seconds if the irradiance is changing rapidly.  I would therefore have expected the archive data to be an average over the archive interval.  However, that seems not to be the case and the archived value is simply the sensor reading at the one-minute time-stamp (see attached plot - particularly the 11:30 - 11:31 interval).  For longer archive intervals it may well average over the "on the minute" values and that definition of averaging would of course also fit my one-minute archive - except I suggest an average of one value is not making full use of the data!  Is this interpretation of what the software is doing correct?

Also as a supplementary question - when and if it averages the 5-sec temperature data samples correctly to what interval does a one-minute archive interval time-stamped for example as 08:01 refer?  Is it
08:00:00 - 08:01:00
08:00:30 - 08:01:30 or
08:01:00 - 08:02:00  or none of these?!

Thanks


PS apologies if the plot is not inserted or attached but I can't seem to get any indication from the message composing page, even in preview mode, that anything has happened or been accepted when I select an image to attach.

[Skywatch]

By sun sensor is it a solar or UV sensor? The temperature sensor(s) update 10 seconds. Solar and UV updates about 50 seconds. The update interval in WeatherLink depends on what logging interval you have the logger set to. If you have it set for 1 minute each data set is every 1 minute and independent of the actual sensor transmittion. Additionally WeatherLink logs the highest or peak reading per interval for solar, temperature, wind and a few others which I think you maybe refering too.

I'm a little confused about the last question. Temperature updates 10 seconds.

Hope this helps.

[dalecoy]

...well, you could ask Davis for an official answer, and post that here.  But:

A.  It seems clear from your graph that the archived solar reading is the instantaneous value at the time that the logger records the data.

B.  I'm rather confident that, for those parameters that are averaged, the average logged represents the interval that ends at the time the logger records the data.  In other words:  08:00:00 - 08:01:00.

I would also point out that, regarding the solar data, if you moved the sensor laterally a short distance (say 1 meter), the instantaneous variations due to cloud movement (etc.) would be quite different.  So, given that as well as the usual usage of solar data (total watts per square meter per day), short-term averages probably aren't that significant.

[C5250]

B.  I'm rather confident that, for those parameters that are averaged, the average logged represents the interval that ends at the time the logger records the data.  In other words:  08:00:00 - 08:01:00.

This is correct if log averaging is enabled, if not the logged value of temperatures is the instantaneous value at the end of the logging period.

[Onepk]

Thanks for the replies.

"By sun sensor is it a solar or UV sensor?"  Yes, sorry I meant solar (broadband) sensor.

"Solar and UV updates about 50 seconds."  Yes, thanks, I now see that is obvious from the console data, but not given in the WL help info.

"Temperature updates 10 seconds."  Ok, maybe I misread the info and the 5 secs applies to consoles only, with nothing indicated for archived data.

"...well, you could ask Davis for an official answer, and post that here.  But:"  If only!  I emailed Davis "support" 10 days ago but they haven't deigned to reply so far.

"In other words:  08:00:00 - 08:01:00."  OK.  If I download and list the archive immediately after 08:01 is shown on the console, the archive already contains the data for 08:01, which fits.
 
"I would also point out that, regarding the solar data, if you moved the sensor laterally a short distance (say 1 meter), the instantaneous variations due to cloud movement (etc.) would be quite different."  True, and that leads onto my next question...later, but footie is about to start!

I guess in this case I can conclude that the WL help-info statement

"The value logged by WeatherLink is the average solar radiation measured over the archive interval."

is not the whole truth in the 1-minute limit, but maybe 50/60ths of the truth!