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By RegisteredJack45
I'm researching my sensor options for taking external temperature, pressure, and humidity readings on my high altitude balloon project. We're going to ~100,000ft for ~3hrs flight time. I'd like to know if anyone has any good ideas as to which sensors would be a good pick, and which sensors I'm eyeing would be a bad pick. I want to take a few of each sensor that are commonly used and compare the results.

Since I'm looking to read external data, the sensor needs to be compatible with conditions as low as -60ºC. That's sort of the kicker and what makes some of the more commonly used sensors incompatible with the mission.

For IC based temp sensors I'm seeing most are incompatible with that low of a temp except the TMP102 which is good to -55ºC. It looks like a RTD or thermistor would fit most options at that low a temp, which requires as little as a voltage divider circuit to get an Arduino compatible input.

For pressure the sensor I'm liking most is the Honeywell ASDX series, good down to 10inH2O/2.5kPa and they have a tube for a hose to take external readings- the chip itself is only rated down to -20ºC but the hose attachment cures the problem. I'd like to compare to to the more commonly seen MPL3115A2 and even the BMP180 which has a pressure ceiling of about 9km (we're going to 30km) yet people still use them in HAB projects for some reason- I'd like to use one just to compare it's graph to sensors rated for the project.

For humidity, I'd like to see some advice because I'm having trouble finding something that'd work below -40ºC and viable as an external sensor. I'm looking at using the commonly used HIH-4030 alongside an HIH-4031 to compare data, theyre the same except the HIH4031 is hydrophobic coated and more compatible with moist environments yet SparkFun decided to put the HIH4030 on a breakout instead for whatever reason. I also want to use a DHT22 because it'd be an easy addition and this sensor is cheap and adorable.
I was able to find one humidity sensor on DigiKey (HPP804B130) but it's not on a breakout board and would require a custom circuit not necessarily outside the scope of our capability but outside of the time we're able to put into it.

Here's the list I've come up with

As far as other hardware, I'm using an Arduino UNO R3, an Energizer LA522 Lithium 9V (it's good to -40ºC, 30g, and 1000mAh!), an Adafruit Ultimate GPS Board (which will give me altitude data to convert to theoretical pressure to compare with the actual pressure data), and I cant decide if I want the Logomatic V2 or the Adafruit Assembled Logging Shield.

Your sensor input (no pun intended) is appreciated.
Have you searched for what others have used in high altitude balloons?

It will not be just the sensors that will have issues with the extremely low temperatures. The computer chips, memory, radio, etc will also have issues.
What I have seen done is putting all of these electronics items into a insulated box (Styrofoam) and adding a heater.
This would work for the pressure sensor but maybe not for the humidity sensor to get correct measurements.
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