Telemetry logs "oddity"

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PeterV
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Telemetry logs "oddity"

Post by PeterV »

I am not sure where the issue comes from but in the Companion Log Viewer - all versions 'forever' - I have always been shown a chart of the values with a "wave" in them. The wavering value is certainly not what truly happened during the flight it was recorded.
This applies to pretty all all (ALL?) telemetry data.
See the pics below:

Is there a reason for this result?
Does everyone have this same issue?
Even the TX ELE( elevator) graph has a constant waver of up and down.
Attachments
VFAS steps.jpg
Ele wave.jpg
Baro Alt wave.jpg
Airspeed wave.jpg

Carbo
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Re: Telemetry logs "oddity"

Post by Carbo »

Every plane oscillates and maybe the elevator log shows your effort, to stabilize the flight.

https://en.wikipedia.org/wiki/Phugoid

On the other side, your logged oscillations are very high, can you describe the model and the telemetry you used? Is the logged altitude realistic (sometimes <0)? Do you have a value in the ratio field for altitude?
To be sure, that there is no other influence, make a log with the plane lying on the table. The Frsky/opentx telemetry is very reliable, i had never any issues with it.
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jhsa
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Re: Telemetry logs "oddity"

Post by jhsa »

The Elevator log has nothing to do with telemetry..
His hand would have to be shakin at about 7 or 8 times a second to produce that result on the elevator. One thing that comes to mind is jitter on the controls. But it appears to show on every log?
I'm commenting on this but I don't use openTX, so I can't do any testing..

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Kilrah
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Re: Telemetry logs "oddity"

Post by Kilrah »

jhsa wrote:His hand would have to be shakin at about 7 or 8 times a second to produce that result on the elevator.
Uh no, if you look at the time scale it's about 4 oscillations per minute, slow enough not to notice you're doing that.
The other logs even make sense given this, and the relation between elevator action, alt and speed seem to match.

Note that depending on your sensor install the actual alt/speed changes could be kinda amplified due to pressure buildup in the fuselage.
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jhsa
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Re: Telemetry logs "oddity"

Post by jhsa »

Ok, I counted the half cycles instead of the full cycles. That gives about 4 yes.. But for your hand to shake at 4 times a second, you might have to be very nervous :)
A good test is as mentioned before to log with the plane on a table.. Then compare the results.. :)

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Kilrah
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Re: Telemetry logs "oddity"

Post by Kilrah »

4 times a minute for the large oscillations. The small moves on top of that are just normal movements.
PeterV
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Re: Telemetry logs "oddity"

Post by PeterV »

"4 times a minute for the large oscillations. The small moves on top of that are just normal movements."
What do you mean then?

I fly around extremely smoothly, so there won't be any altitude 'oscillations' created by me - well more stable than the reports anyway... or Elevator usage to match what the graph shows.
I also do not fly the 'same pattern' over and over and over to have such a good timing cycle! The flight path can be 'all over', changing 'straight' lengths, turn periods and/or arcs etc. Those differences are going to be way different to '4 times a minute'. There is no way there will be any 'consistent' time cycle - or even somewhat consistent.

But setting it stationary is a somewhat of a good idea to test.... but might mist out on the issue if it is linked to amplitude of a value. eg at zero it will have error multiplied by zero anyway.

Every single log file I have does this, even back in Er9X I am pretty sure. It started when I got some barometric sensors about 4 years ago and I saw the log results and wondered why - and was disappointed in the 'half uselessness' of it.

Even when flying, the Speech readout 'captures' a moment in time that it will queue up to report.... so you can be flying around very level in altitude and get a value anywhere from that 'wave' graph. eg 50m one report, and 45m the next, then 52m... whilst flying level. It just depends what moment it catches the telemetry 'wave' at. High.. low... medium.... anywhere....

At first I thought it might be linked to just the Barometer and pressure.... and I didn't even think about checking other Telemetry values. Or I think I even saw others WERE stable at that time, thus I thought it was Barometer sensor created (and I contacted them).
I will go over old logs (years old) to verify what other Telemetry parameters were not stable, and if that changed 'one day' along the way - maybe with a certain version of OpenTX onwards.

PS: My glider has this wavering outputs too... yet it is flown along EXTREMELY linear and smooth, as typical for a glider. Trying to maintain 'perfect' stable flight. And it is FPV, so I am "IN" the plane and can see what level of instability it is going through - and me correcting for. (I have not looked at its Elevator/control telemetry ever). Via FPV is usually far more stable than LOS flying.
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Kilrah
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Re: Telemetry logs "oddity"

Post by Kilrah »

PeterV wrote: And it is FPV, so I am "IN" the plane and can see what level of instability it is going through - and me correcting for. (I have not looked at its Elevator/control telemetry ever).
That's great, do you have a full (unedited) flight video of an affected flight posted somewhere we can look at?

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