PreArm: Accels Inconsistent

After upgrading to 3.2 i can´t arm the copter if temperatures are belov +5 Celsius. I had no problems with 3.1.5 when there was -15 Celsius. I have tried 3 different boards. 2x HKPilot32 and 1x original 3DR Pixhawk and all have the same issue with 3.2 firmware. 2 were quad copters and one was octocopter. I can skip the INS prearm check and it flies like a bird but this is not a real solution. I think that this is a very annoying bug in the 3.2 firmware. Is there anything that I could do or try?

Hi Paul,

There is a real issue here, I have experienced it on one board myself. The accelerometers really can experience accel bias inconsistency due to the temperature.

Question, are you allowing your systems to acclimatize to the temperature outdoors for a period of time before power up? If not, you should. That might just be your problem. If you boot up while warm, then take them outside, wait a few minutes, then try arming, that is not the correct way to operate. You need to take them outside unpowered for at least 5 minutes, let them cool down. Then boot up.

If you are doing it the correct way, and you have 3 boards with the problem, that is curious. I have 1 out of about 10 Pixhawks with this problem. And we have very little data on this problem so it must not be common.

If this is the case, can you take your Pixhawk, set the Logging to “All+Disarmed”. Then go through your normal boot sequence and get me the logs please. I’d like to have a look.

Part of the problem is that we have no data on what is an acceptable amount of inconsistency to allow a flight. Thus, we have been conservative.

I let always the system acclimatize because it flies much better then. If I bring it outside and let it acclimatize then the problem always occures. Once I got it to work when i did breathe warm air on it. Now I tried 2 times logging it but it does not log. It only logs when i have powered it through usb and mission planner running. I tried 2 times and always the same problem. I will trie it again today.

Today i disabled the INS prearm check and then I also got a log file.
Link for logs: