I've been bench-testing my APM2 board and everything is working well enough but I'm noticing an issue with the altitude reading; it's all over the place!
After initial startup the APM2 usually starts with an altitude reading around 8ft (not zeroed at startup). From that point on the reading ranges between all sorts of values. It seems like at first the reading will climb (not steady, but overall) until it reaches another +4-5ft then starts wildly bouncing between 8ft-14ft and sometimes dropping below 8ft to as low as 6ft. That's a huge margin of error for a sensor that's supposed to be +/- 10cm! All my bench-tests have been indoors in still air (my APM is also enclosed in the DIYDrones case). I'm concerned this could become a major issue when I get to using the autopilot functions on my aircraft.
Is this normal or is my board faulty? Are there some tweaks/PID settings I've missed that would help get a more accurate altitude reading? What about the altitude being zeroed at startup? Please help! I would like to have at least a +/- 12in. accuracy before I put this in my plane.
Thanks in advance.
Replies
The "altitude" reading will change for a given location as the barometric pressure changes i.e. the weather. Good luck if you think you're going to get an altimeter that's accurate to within a foot for $200, never mind attached to an APM for that price. Resolution may be much less than a foot, IDK, but accuracy? People here tend to use sonar for accuracy at low altitudes. Your pressure sensor sounds normal to me.