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Taranis Plus Telemetry Accelerometer Logging Scale - HELP

#1
I recently got the telemetry logging to work on my Taranis Plus and was excited to see how many Gs I was pulling on hard turns with my racing quadcopter. Unfortunately, the accelerometer data is not scaled properly, it is responding correctly to movements, but the resting z-axis force is measuring 0.46. According to everything I can find so far, this should be reading 1G for the downward force of gravity. Does anyone know what scale factor to apply to convert into m/s^2 or Gs so I can get usable data from my Taranis?

Setup:
AfroFlight Naze32 Rev6 - Betaflight Naze 3.0.1
FrSky XSR Telemetry RX
FrSky Taranis X9D Plus TX

Running telemetry through UART1/Smart Port on the Naze.
 

Craftydan

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#2
Sitting flat on the table, measure the Z axis. Turn it over, measure again.

The difference between the numbers is 2g, so the "g" scale will = (2g/measured difference).
 
#3
Sitting flat on the table, measure the Z axis. Turn it over, measure again.

The difference between the numbers is 2g, so the "g" scale will = (2g/measured difference).
Thank you so much, this seems to have worked perfectly. Here is the result from one of my flights. It seems to peak at 4.5Gs and rests at 1.

Acceleration Z.JPG

One last question, is there an equivalent way of converting for X and Y? When applying this formula on them, it gives -1 for X at resting, which should be 0.
 
Last edited:

Craftydan

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#4
Since the sensor is a 3-axis package (really 6, but you get the point), they should all scale to the same value.

If you want to confirm . . . set it on it's side. Rinse, wash, repeat.
 
#5
That makes sense, thanks so much for the information, I have been looking for a solution for several days now and staring at 3 axis accelerometer datasheets was getting old.
 

Craftydan

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#6
No worries. I was half-way through a masters program before figuring this out (back in the day when we made accelerometers out of bear skins and rocks -- the data sheets haven't gotten much better).

I'm occasionally reminded the obvious is only obvious once you know it ;)