13,000ft Flight - Sensor Failure

Over the weekend I did my first Balloon assisted flight.  Helium balloon carried my glider up to 13,000ft, at that point i issued a remote cutdown command to release the balloon from the plane.  

 

http://twitter.com/#!/W0OTM/status/130798913224577024/photo/1

 

We ha some issues...First know that shortly after launch the XMTR was turned off, to initiate RTL mode.  So, for the majority of the flight (20min) it was in RTL mode while suspended from the balloon.

 

After finding the wreckage, I began to filter though the logs.  (the APM survived the crash)  Here is what i found.

 

The pressure sensor began sending erroneous readings as 1137m (4,000ft) or so.  Here is a sample of the logs.

 

GPS: 71299000, 1, 11, 41.1029510, -92.4485240, 0.0000, 1137.9200, 1294.2400, 2.2300, 338.1000

GPS: 71299000, 1, 11, 41.1029510, -92.4485240, 0.0000, 950.5000, 1294.2400, 2.2300, 338.1000

GPS: 71299250, 1, 11, 41.1029590, -92.4485240, 0.0000, 821.7400, 1296.0200, 1.9200, 18.2300

GPS: 71299250, 1, 11, 41.1029590, -92.4485240, 0.0000, 650.5400, 1296.0200, 1.9200, 18.2300

GPS: 71299250, 1, 11, 41.1029590, -92.4485240, 0.0000, 452.5100, 1296.0200, 1.9200, 18.2300

GPS: 71299500, 1, 11, 41.1029590, -92.4485170, 0.0000, 238.2400, 1297.8101, 2.3700, 38.0600

GPS: 71299500, 1, 11, 41.1029590, -92.4485170, 0.0000, 15.0300, 1297.8101, 2.3700, 38.0600

GPS: 71299750, 1, 11, 41.1029660, -92.4485170, 0.0000, -137.8500, 1299.6100, 2.8800, 55.0100

GPS: 71299750, 1, 11, 41.1029660, -92.4485170, 0.0000, -316.5000, 1299.6100, 2.8800, 55.0100

GPS: 71299750, 1, 11, 41.1029660, -92.4485170, 0.0000, -439.2400, 1299.6100, 2.8800, 55.0100

GPS: 71300000, 1, 11, 41.1029700, -92.4485090, 0.0000, -523.8900, 1301.4301, 3.1900, 61.0800

GPS: 71300000, 1, 11, 41.1029700, -92.4485090, 0.0000, -582.4400, 1301.4301, 3.1900, 61.0800

GPS: 71300250, 1, 11, 41.1029700, -92.4485020, 0.0000, -623.2000, 1303.2400, 3.6500, 58.7000

 

Also, the IMU axis sensors stopped sending values at 7000ft.  Also note the HUGE difference in the MIXALT and the GPSALT.

 

GPS: 71460500, 1, 10, 41.1069680, -92.4342270, 0.0000, 140.1700, 2359.3101, 15.8400, 99.1400

ATT: -17273, -7770, 1014

GPS: 71460500, 1, 10, 41.1069680, -92.4342270, 0.0000, 140.7600, 2359.3101, 15.8400, 99.1400

ATT: -16141, -8484, 35974

GPS: 71460750, 1, 10, 41.1069640, -92.4341740, 0.0000, 141.4400, 2360.8999, 15.1800, 100.5000

ATT: -11298, -8952, 31063

GPS: 71460750, 1, 10, 41.1069640, -92.4341740, 0.0000, 141.8600, 2360.8999, 15.1800, 100.5000

ATT: 0, 0, 0

GPS: 71460750, 1, 10, 41.1069640, -92.4341740, 0.0000, 142.5400, 2360.8999, 15.1800, 100.5000

ATT: 0, 0, 0

GPS: 71461000, 1, 11, 41.1069560, -92.4341280, 0.0000, 143.3000, 2362.7300, 14.6200, 101.7700

ATT: 0, 0, 0

 

What would have caused these 2 failures? 

2011-10-31 11-32 1_edit.log

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Replies

  • cosmic rays ;) just kidding

  • Sort of on the subject of the pressure sensor (which drives the non GPS altitude), the data sheet says that the hole in the top should not be exposed to light (during reading) as it can "influence the accuracy of the measurement". I thought that was interesting for those that mount their APM board facing the sky.

    http://www.sparkfun.com/datasheets/Components/General/BST-BMP085-DS...

    page 25.

     

  • Hello to 

    Ottumwa, IA

     

    Barometer problems could be due to temperature extremes and wind.  It's recommended to cover it with a piece of foam.

  • Marshal I have experienced something very similar around the same altitude.
    I have replicated it twice.

    Around 1300m, my APM started reporting -1000m altitude (so of course started climbing).

    Details are here...

    http://diydrones.com/forum/topics/nasty-altitde-bug 

This reply was deleted.

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