Vertical speed sensor? (variometer?)

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Matteo April 29, 2018 at 1:30am

Hi friends some news abaut vario on 3dr?Ì use from long time this autopilot for make fpv long range and i ask if is possibile use audio input for trasmit to the ground one variometer signal
Jeff July 28, 2014 at 12:06pm

A resolution of 0.1 knot is impressive Marc. Can you describe the specialized code you use to pull the signal from the noise?
- Marc Ramsey > Jeff July 29, 2014 at 11:56am
  
  Jeff, did you notice this thread is nearly 6 years old?
  
  By "specialized" I meant specific to the implementation of a variometer. In our case, using the microcontroller onboard ADCs and digital filters, combined with simple linear boxcar filtering in the code was good enough to achieve that level of resolution on a desktop. In a glider we use the variometer in conjunction with a total energy compensator, which mixes altitude with airspeed to calculate total energy altitude, either before the variometer pressure sensor sees it (using a pneumatic compensating probe), or in the variometer code (using airspeed sensor data). When in turbulent air, a glider encounters horizontal gusts, causing transient fluctuations in airspeed which, in turn, show up as (sometimes large) fluctuations in variometer reading. This was addressed by implementing a "gust filter" as the final step in the variometer code. We tried a variety of filter implementations, but simply rate limiting the change in variometer indication was sufficient to damp down the transients, while not interfering with the all important task of finding rising air.
Marc Ramsey September 1, 2008 at 4:04pm

What you're looking for is called a "variometer", which is a sensitive vertical speed indicator. There are miniature ones intended for use in R/C sailplanes, but these typically transmit an audio tone to a ground based receiver, so they would require some adaptation if you want to use the signal on-board the helicopter.

I've able to measure vertical speed down to a resolution of less than 0.1 knot (5 cm/sec) using an absolute pressure sensor, 24 bit A/D converter (needs about 18 to 19 bits effective resolution), and digital differentiation, but it takes a lot of specialized code to separate the signal from the noise...
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Chris Anderson September 1, 2008 at 8:12am

I can't think of any. The usual speed sensors (pitot tubes) won't work in the vertical dimension on a heli because of propwash. I think this is something you'll have to derive by integrating your static altitude measurements over time.

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Vertical speed sensor? (variometer?)

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