How fast do Avata motors rotate?

[BudWalker]

I'm updating CsvView/DatCon to include Avata specific data. At idle without props my Laser Tachometer says the rotational speed is 4680 yet the .DAT says it's 530. This is unlike all the preceding DJI platforms where the .DAT accurately reflects the speed measured by the Laser Tachometer.

Does anyone know how fast these motors rotate?

 

[rktman]

I think you instrument is faulty... there's no way they're spinning at 4680 rpm at idle. I'd go with the 530 as correct.

Let your ears be your check – 4680 is a pretty high pitched whine, which you hear props or not. It will just be a lot quieter.

 

[BudWalker]

I think you instrument is faulty... there's no way they're spinning at 4680 rpm at idle. I'd go with the 530 as correct.

Let your ears be your check – 4680 is a pretty high pitched whine, which you hear props or not. It will just be a lot quieter.

Thanks for responding. It's been a while since I thought about this.

This morning I did the same test with my FPV and the motorSpeed data agrees pretty well with the Laser Tachometer. Here is the motor Speed data showing the front motors idling at 4500 to 4700 rpm. This agrees with what I saw on the Laser Tachometer


I also looked at the Mavic2 idling motorSpeed which was around 3000 rpm. From this and the FPV motorSpeed data I'm more inclined to believe the 4680 RPM values shown by the Laser Tachometer. 530 RPM seems way too low.

 

[rktman]

Interesting! A bit of a mystery then... here's a 4khz tone, and none of my drones sound that high pitched at idle. I don't doubt your data, just scratching my head regarding the sound and physics

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Are you measuring the blades with the tachometer? The RPM would then be ÷3 for the FPV, and ÷5 for the Avata.

But then there's the logs... Hell, I don't know!

As part of the tone "sanity check", remember that a doubling of frequency is an octave increase in pitch.

 

[BudWalker]

Interesting! A bit of a mystery then... here's a 4khz tone, and none of my drones sound that high pitched at idle. I don't doubt your data, just scratching my head regarding the sound and physics

Freesound - 4000hz.wav by mjscox

Freesound: collaborative database of creative-commons licensed sound for musicians and sound lovers. Have you freed your sound today?

freesound.org

Are you measuring the blades with the tachometer? The RPM would then be ÷3 for the FPV, and ÷5 for the Avata.

But then there's the logs... Hell, I don't know!

As part of the tone "sanity check", remember that a doubling of frequency is an octave increase in pitch.

For the Avata I taped a white piece of tape on the hub and had the props removed. For the FPV it was a black piece of tape on the hub with props removed.

 

[rktman]

That should do it.

Granted, a laser tachometer is probably more accurate than my audio tachometer, which admittedly is a much much older design...

 

[Barbara]

Just curious, why measure the rpm with the props removed?

 

[BudWalker]

Just curious, why measure the rpm with the props removed?

So that it doesn't take off while I'm taking a reading at the higher revolutions. Also, wanted to make sure the Laser Tachometer wasn't reading the prop blades instead of the stripe on the hub.

 

[Barbara]

So that it doesn't take off while I'm taking a reading at the higher revolutions. Also, wanted to make sure the Laser Tachometer wasn't reading the prop blades instead of the stripe on the hub.

Makes sense, but would be interesting to see how much slower the rpm would be with the blades on.

 

[Kilrah]

Makes sense, but would be interesting to see how much slower the rpm would be with the blades on.

The goal was to correlate the real rpm reading with what shows up in the logs.

 

[Barbara]

The goal was to correlate the real rpm reading with what shows up in the logs.

Ah, yes, ,I understand. Reread the thread from the top. I don't think I've ever gone into the DAT files. Normally just save the Flight Logs and really, I only look at them if something unusual came up during a flight. I understand there is much more data included in the DAT files but have never had occasion to look.