It is not always what you think it is …

Last Sunday the local time changed from summer time to winter time. For the scheduler that I use in my weather station software this is a critical test. So, that morning I was watching the records sent to Weather Underground and to the log files I record myself. To my great suprise a serious hickup was signalled: temperature and pressure values about three times their normal value. Starting around 2 am and disappearing around 3 pm. After that, the station reported as if nothing had happened before.

I tried to look at the recordings in different ways but I could not find out what had gone wrong. Nothing in relation to the time change. In particular I was curious about the reason for temperature and pressure values being that high. I could not find anything peculiar and after restarting the station I left it alone. Of course more curious now to see if the hickup would repeat itself. Nothing of the kind though.

Suddenly, Wednesday morning it occurred to me that the solar radiation values remained zero: apparently these were no longer measured. There was no time to immediately take action and for the rest the weather station was working perfectly so I let be. I did realize that the sensor could have broken down and in that case I needed to replace it. Of many parts of the hardware I have a duplo but not of this one, so I ordered one. It only costs a few euros and the same amount on postage.

solar_radiometer

Friday afternoon, the new sensor arrived and there was time to take the instruments inside the house. Quickly it appeared what had happened, see photo. When I saw the device I remembered that I was worrying about the exposure to environmental conditions. It should be packed better. For the time being, I just put the new one in a little plastic bag. That should protect it for a few months. The former one survived for about half a year! Also, I noticed that the plastic lens that is put in front of the sensitive windonw (yellow on photo) was yellowing. Clearly, a better design is needed but for a while the replacement will work well. Winter time should not be too rough on the sensor albeit that temperatures might go a bit out of the acceptable range. We shall see!

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