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Where is the barometer / Altitude trouble

Discussion in 'Pro/Adv Discussion' started by FredzMaxxUAV, Nov 24, 2015.

  1. FredzMaxxUAV

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    Does anyone know where the barometer is in the Phantom 3? Is it inside the VPS module?
     
  2. III% Streve

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    Its likely on the main board. But just guessing. The VPS system is all about cameras and sonar. It would be poor designing to have the barometer there.
     
  3. Meta4

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    It's in the flight controller on the main board and it's likely that your IMU recalibration will fix it.
     
  4. FredzMaxxUAV

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    So I did a cold IMU calibration. Now after 20 minutes of hovering above grass, with moderate wind, the difference is 2 meters instead of 10. But my old P3P only has a difference of 1 meter. Is this acceptable?
     
  5. FredzMaxxUAV

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    Flew again, it was off again by 10 meters. Is this normal?
    I did a cold IMU calibration once more.
    Current values after the calibration are:
    Gyroscopo: all 0
    Acceleration: 0 0 -1 1
    Compass: -577 -597 1147 1415
    This is when the bird is level.

    Is there anything else I can try. Or is the barometer just not that great on some models? My old P3P was rock solid there...
     
  6. III% Streve

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    Compass MOD value is strangely low, but could be ok
    Acceleration should be at ZERO if its not moving It think, but I dont have mine in front of me to check
     
  7. alokbhargava

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    GPS is the main sensor to get the height estimations. VPS system too can calculate heights but it is effective only up to about 3 meters and provided ground surface is good. There are many restrictions on ground surface. It has advantageous only in case one is unable to get enough satellites locked to get proper location.
     
  8. FredzMaxxUAV

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    I thought the barometer, not GPS or VPS, was mainly used for altitude. Am I mistaken?
     
  9. III% Streve

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    GPS supplements the barometer. It is not primary. VPS takes over below 3 meters
     
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  10. FredzMaxxUAV

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    What would be good values?
     
  11. III% Streve

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    Mine, while in the house, are almost exactly the same. Personally, I dont like a compass MOD value outside of 1500+/- 40. But the real answer is far more open. I think the sweet spot for my P3 is somewhat based on my location. Leading to a thought that everywhere in the world will have different "sweet spots" and likely are going to vary also because all compasses cant be perfectly identical
     
  12. Oso

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    This is what I was told by one of the mods (now gone) when I first joined, so this is what I have posted numerous times when asked.

    Gyroscope Mod should be around 0.00
    Acceleration Mod should be around 1.00
    Compass Mod 1400-1600
     
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  13. N017RW

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    Unless there has been a documented change... GPS has never been used for altitude in the Phantom series.

    The Phantom only need know it's height relative to take off thus a barometer is fine.

    Remember the price-point for this flying camera is very low.
    DJI's top-tier FC is more than the P3s in total.
     
  14. FCPhantom

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    I asked it from DJI and they said it is barometer's feature. The barometer has 2cm/s of error.
    If the flight time is 25min = 1500s, then the error can accumulate approximately to 30m = 2cm/s * 1500s
     
  15. Mako79

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    Make sure the phantom has been off for an hour or so. Do the calibration at night when its cooler. Do the IMU calibration the moment you turn on the Phantom. The cooler the phantom, the more accurate the barometer will be. And there is no need to place phantom in the fridge.
     
  16. Mad_angler1

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    baro is located on the bottom of the FC daughter board, you can see it from the battery bay located next to the SD card :)
     
  17. FredzMaxxUAV

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    #17 FredzMaxxUAV, Nov 26, 2015
    Last edited: Nov 26, 2015