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AirGradient Forum

Open Air has trouble with winter?

#1

This morning I was surprised to see that my Open Air disagreed dramatically with my LaCrosse outdoor thermometer by 10 degrees F!

The outdoor temperature was just below freezing (31°F) but the Open Air reported 41.5°F. I double-checked, and the Open Air was in shade, so it wasn’t a matter of direct sunlight heating the enclosure.

Then, looking over the past week’s data, where we’ve had multiple nights below freezing, I discovered that the Open Air has never reported a temperature below 41°F.

Perhaps it’s generating too much heat to provide accurate temperature measurements in colder settings given its enclosure? There probably aren’t too many freezing nights in Thailand, so I can understand why this might have been missed… :slight_smile:

Or maybe it’s just mine?

#2

@pcag

The active components in the enclosure influence the readngs of the temperrature and humidity sensor which is inside the PM module. So far we have seen larger disagreements primarily on the humidity measurements and already developed a compensation algorithm.

I wrote about it recently in our blog.

In Thailand we don’t see much difference on the temperature side. But in colder climate zones it seems to be an issue. Here our comparison we currently do at the University of Cambridge.

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(Open Air in red, Reference in blue)

We see very well that the delta increases with colder weather.

I talked with our in-house scientists and they believe we should be able to generate a pretty good compensation algorithm which we will be working on.

To test it, would it be possible you share your data of your AirGraduent and your LaCrosse? This would be very helpful.

#3

@Achim_AirGradient I’d seen that article on the humidity sensor, but I had assumed that was due to skew inherent to the sensor, so it didn’t occur to me that you might use the same approach to correct for temperature skew due to the enclosure. That makes sense, though.

I’d be happy to share the data. Should I email you the serial number of my Open Air so that you can see its readings?

For the LaCrosse, is there some API endpoint you’d like me to send its readings to? Or do you just want me to report occasional readings when I happen to look? Or something else?

#4

Thank you for sharing your data!

Yes for the AirGradient please send the serial number and for the LaCrosse are you able to just send us a csv /Excel file with the data?

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#5

Just set up an outdoor unit today and I am seeing the same thing. Was there ever a fix for this? My analog outdoor thermometer is sitting in the neighborhood of 35°F but I am seeing a consistent reading of 46°F

#6

We just published a blog post about it:

Once we have more data we will apply the correction algorithm automatically.

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#7

I haven’t forgotten about you, I just haven’t had time to set up a little SDR box to capture the LaCrosse readings. That’ll probably happen after the holidays.