SD Card data is missing when PA Flex is used outside

Sensors
1

Hi y’all, I have the following problem and I am wondering if I am the only one:

Situation: I have 6 Purple Air Flex sensors, all equipped with 16GB microSD cards (FAT32, Kingston, industrial grade) for an I/O measurement series, thus 3 of the sensor are used inside and 3 of them outside. Only two of the sensors are registered via WiFi, the others are used “offline”.

Problem: While all indoor sensors are logging all data without any gaps on the microSD cards, the sensors installed outside are only logging sometimes and with big data gaps (multiple hours, multiple days) on the microSD cards. Thus, the problem occurs only when the sensors are installed outside. I am not sure if this might be a possible reason but it definitely correlates as there no problems with sensors installed indoors.
When I check the data of the one sensor that is equipped outdoors and sending data to PurpleAir.com there are no gaps in the time series.
Thus, I am confident that there is a problem with the data logger.

I tried the PurpleAir tool to recover data from log or txt files without success. The data is missing. If the data would not be visible at PurpleAir.com I would expect a power outage.

Any ideas why that problem occurs (only outside)? And how to fix it?

Thank you and Cheers, Martin

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We have seen reproducible SD card logging failures when deploying PA-flex in cold (New England winter) weather. We make sure they are warm (inside) first, then immediately deploy them outside. Once they are working they continue to work even in very cold wx as long as power is not interrupted. If they are deployed cold [and thus not logging to the SD card], they start logging when the weather gets warm (> 50-60F?). This is reproducible across many (>10) PA-flex.

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4

Thank you George Allen, that is some helpful information. The sensors were running outdoors during a rather cold period below 10°C (50F). Although I would not consider this a very low temperature, there seems to be a correlation with the behaviour of your sensors.

I will make some tests with pre-warmed sensors before deploying them outside!

Thanks again,
Martin