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The "mystery" of the temperature peaks solved

A project log for µPower (beehive) SD logger

Let's observe an emerging beehive throughout the year 2018! (And create an logger from scratch for that purpose)

JanJan 02/03/2019 at 12:252 Comments

So, in the last update I mentioned strange temperature peaks on some days around noon in the outer temperature chart.

It jumped from -7°C to +9°C (green line) here:

What made me wonder is the small peak before the main peak. I thought this can't be a environmental cause then.

But today I managed to get to the hives on a cold but sunny day. Turns out, it's been the sun :)

The small peak before is because the sun finds a small gap between the houses surrounding ours to shine on the outer sensor. Then, a shadow shades the sensor for a longer period and after that the sun shines on the sensor for quite a while.

By the way: thanks to the people in the hackaday.io chat. They did everything to convince me it's a natural cause. I'm looking at you @Morning.Star and @anfractuosity :)

shadow on the sensor, moving to the right
sunshine responsible for the bigger peak

On another note, we moved the hive to the later position in summer. Here's how the stand looks like after moving it:

That light brown stuff is the bees waste. It's exactly where the winter cluster sits.
position set for summer

The new position will be in direct sunlight a bit later, so the peak (if any) will move to a later time each day.

Discussions

Xasin wrote 02/03/2019 at 14:44 point

It's always both a little weird and cool to discover that what first looked like erroneous readings were just caused by more precision than expected. Maybe a small reflective covering around the sensor casing could prevent the sun from heating it up that much? Or a small fan gently blowing air through it to keep it at ambient.

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Jan wrote 02/03/2019 at 15:52 point

Hi Xasin and thanks for your input!
Fan is out of question, the logger is super low power. To get the "real" outside temperature, the case should (at least) be shaded and the case vented...

But I won't do that with this one as I' ll be switching to the next version before the new season starts (around March). Together with the sensors the bees will build into their combs!

The external sensor will be in a proper place then.

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