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Comment by ClosedPistachio | Hacker News Reader

Any recommendations for a good portable CO2 monitor?

> "Connect your device to the app to view, track and analyze your data from the last 7 days"

In a time where gigabytes are trivial (megabytes is enough for hundred thousands of measurements anyway here), why do such limitations like "7 days" still exist?

If there's a way to get a CSV or similar file you can analyze on any device you want, then we're talking

I can’t speak to why there’s a limit but you can export your history as a CSV from within the app: as long as you export at least once every 7 days, you’d have a full history through the life of the device.

The CSV contains datapoints for each recording (default to 5 mins but use configurable): Time(dd/mm/yyyy), Carbon dioxide(ppm), Temperature(°C), Relative humidity(%), Atmospheric pressure(hPa)

I’m very impressed by the device and recommend it.

That's actually pretty nice, only a shame since I still find that 7 days is a short timespan to require manual action for something otherwise nicely automated

There's several Python scripts that can pull the data over Bluetooth.

https://github.com/stijnstijn/pyaranet4

https://github.com/Anrijs/Aranet4-Python

Don’t diabetics monitors do the same thing to make sure you keep paying?

You could also get a CO2 sensor from Adafruit for $50, connect it to an Arduino, Raspberry Pi, or other controller, and roll your own solution. It's a little hacky, but this is HN after all. https://www.adafruit.com/product/5187

I can't speak to the accuracy or quality, but there's plenty of dedicated CO2 monitoring devices on amazon for under $100. A few seem to have good reviews, anyway.

I have a couple (either 2 or three, i can't remember) from amazon that were under $100. Both have built in batteries, and one is designed to be charged and then placed in a greenhouse while you're working in it, another is designed to reference between two "rooms" or whatever.

None of them log to sd card. I'd fully expect a functional solution that does logging with all of the other features to cost more than $100, but if i can be proven wrong, i'd buy one, for sure.

For example, with an SD card we now also need a clock - which ideally would have a different power supply than the sensor suite, otherwise the timestamps will overwrite if the supply is lost, or otherwise be incorrect.

I was going to comment on accuracy, but looks like this one is actually pretty good!

Definitely the same ballpark as ara4. (I mean, building the thing would subtract several hours of time one could spend commenting on HN instead, so choose accordingly :)

It looks like a product design "feature" - they sell a "pro" version that works with their $600 base station to upload data to their cloud service.

If the home device gave unlimited history, then there'd be less incentive to buy the pro version and subscribe to their cloud service.

Shameless plug.

We are maintaining an open source / open hardware indoor air quality project that measures CO2, PM2.5, temperature and humidity [1].

We use the same CO2 Sensor (Senseair S8) as the device in the article and I can confirm that it's very accurate.

[1] https://www.airgradient.com/diy/

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