Flytrex barometer issues

JKDSensei · Oct 25, 2015

I'm using Flytrex Core 2 and seem to be having some barometer issues.

Wondering if anyone else is having similar issues.
I am near sea level. Maybe 7 feet above.
The reported Maximum Ascent and Maximum altitudes see significantly off.

For example, on one flight, maximum ascent was reported as 247 feet while maximum altitude was reported to be 68 feet. in the Flytrex core data stream, the initial altitude shows as -193 feet.

Not sure how or why it would read minus 193 feet when I'm actually 7 feet above sea level.

That seems significantly wrong.

I have checked to be sure that the port on the back of the device is unobstructed and can get free air circulation.
It is underneath the Phantom so prop wash should not be an issue. The temperature inside and outside was within a few degrees so it shouldn't be temperature related.

Also, it seems to come and go. Some flights have much more reasonable numbers. Others are way off and that trend seems to be increasing.

Any thoughts or suggestions would be appreciated.

PS..I have a support request in to Flytrex...waiting on a response.

JKDSensei · Oct 25, 2015

May also be having distance issues as well. But I do believe that distance information comes from the onboard Naza / GPS.

I've got about 50 flights on this Flytrex Core 2 unit and I'm just getting more inaccuracy at this point than I'd like.

I take off from and land at the same spot with 10 minutes approximately in between.
Today I got a reading that says I landed 115 feet from the start point but that is not correct.
The actual difference was probably 2 feet.

Could be the GPS on the Phantom also but it seems to be getting sat locks quickly and I'm getting as many as 12 sats so it seems more like the Flytrex core 2 is quirky.

bbfpv · Oct 26, 2015

The flytrex just records data from the FC, it doesn't have its own barometer. Assuming your bird's telemetry is showing accurately elsewhere, sounds like an issue w/ the flytrex unit.

JKDSensei · Oct 26, 2015

bbfpv said:
The flytrex just records data from the FC, it doesn't have its own barometer. Assuming your bird's telemetry is showing accurately elsewhere, sounds like an issue w/ the flytrex unit.

Not sure which Flytrex unit you refer to but Flytrex Core 2 definitely has an onboard barometer.

From Flytrex.com website.....

"Although Flytrex Core 2 can be mounted anywhere on the aircraft, for optimal altitude and temperature reading we suggest paying attention to the placement of the barometer component.

The barometer component can be located easily - it is placed on the other side of the microSD and it is the only component with a small hole in it. Check out the included picture with marking the barometer, just to be sure.

This small barometer hole needs to be mounted in such a way that prevent direct sun-light from entering it, yet remain open to air flow. This can be very little air and just shouldn't be completely sealed."

manual_core_screencap_flytrex_core_2_barometer_mounting_mini.png

JKDSensei · Oct 26, 2015

Flytrex seems to start recording the flight data stream shortly after you connect the main battery.
Before it begins recording flight data I believe it checks the SD card then provides a bit of version information....then begins recording flight data.

The problem is, if Flytrex finishes it's startup routines and begins recording flight data BEFORE you have accurate GPS lock, the initial flight data can be off by a lot. At lest related to the distance and horizontal position data anyway. Vertical data is provided primarily by the barometer located directly on the Flytrex unit. So as far as I know, altitude data is pulled from the Flytrex unit.

As far as distance errors....
For example, let's say Flytrex finishes it's startup routines and then starts recording flight data for the current flight and the GPS/Naza has only acquired 3 or 4 satellites. The GPS accuracy at this point will be significantly low. In some of my data streams, as much as 160 feet.

So, now Flytrex has recorded my flight's starting position as 160 feet away from where I'm actually starting the flight.

Maybe I need to do an update but I seem to be running the most current firmware on the Flytrex.

What seems to be an apparent solution is to not power up the Flytrex until you have greater than 5 satellites locked. But it powers off the main battery so that's not the standard setup.