Temperature/humidity spikes at 05:30

Now that I’ve been building a simple solution (blog post coming later) to collect and store RuugiTag sensor data into cloud, I’ve been noticing somewhat weird anomaly with sensor data: Quite often, the temperature and humidity values have a spike around 5:20 (see attached image). Anyone else getting similar behaviour? :thinking:

Despite the background scanning, I’m not getting any results from the same time, but from there can also see the sudden temperature drop after first readings:

Tag is placed outside the house and data is being collected using Rasperry Pi with node-ruuvitag script. There are no scheduled activities in Rasperry Pi, other than restarting the WLAN connection if it drops out.

Also, worth to add: I have three other RuuviTags (all placed inside, though), and I can’t see any value spikes from those. So, I wonder what happens around my house at mornings? :sweat_smile:

Any ideas?

The sun is rising and pointing on the Tag? :innocent:

Tag has some coverage from most direct weather changes, but I guess it is a possibility, yes :thinking:

My bet is the Sun. A direct sunshine in the morning (or any other “heat source”) will sharply increase the temperature and decrease the relative humidity (as it’s directly dependent on the temperature), while the absolute humidity should increase only very slightly (because air and water densities change slightly differently as the temperature changes). The sharp decrease a little time later looks like the tag goes out of direct sunlight at that point, so it may be a short-ish period of time when the sun is able to shine on the tag

Thanks for the replies so far. When looking at the times and the angle, the sun really can be a possibility. Just a bit surprised the temperature can really jump as much as 10C due to direct sun light at mornings.

Will have to collect more data and see if I can reposition the tag even more optimal location :+1:

Any update?

Temperature spikes do not occur daily in the 20 Jun to 2Jul image, rather every OTHER day!

Interesting variation in the timing between samples in the 16:39 to 06:32 image… Can you explain that.

Is the enclosure cover in place?
Is it in a “rain safe” location?

I’ve found the sunrise being very likely reason for those spikes, as proposed earlier. On cloudy days, the change has been smaller or non-existing:

The tag itself is placed on the window frame, being quite safe from the rain:

When it comes to official Ruuvi Station app, the recent update seems to fix the background scanning, so now there are more data points collected with it as well.

Off topic: As it can be seen from the charts, the summer has been quite awful in Finland this year when you’re looking at the temperatures, being July and all. :cold_face:

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As it is “rain safe” it might be interesting to see if temperature’ (i.e. rate of change) is any different with the cover off for a week or so.

Are you open the window when these spikes arrive?:smiley:

As promised, here’s the blog post about the project: