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[F-FT] Altimeter questions

I don't think these are your standard altimeter questions, but here goes...

How many readings (and at what rate) do folks typically store for a flight with an altimeter? How many bits resolution?

Same question for those of you doing motor testing -- when I look at the static test data, the initial spike seems to have very few data points because of the speed which it occurs at. What rate do you typically store this information? To what resolution?

Now, for the kicker -- in a perfect world, how much data would you LIKE to store, and at what resolution?

I'm asking because (eventually) I may design my own altimeter (purely for the heck of it), and I have DECADES of experience with low-power high-speed data capture devices (designing them, not just using them). So, I'm trying to figure out of one of my existing projects (re-laid out on a new PCB, of course) would do for this type of project.

David Erbas-White

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David Erbas-White
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Hmmm.... this varies with different products: the AltAcc does 8-bit samples at 16 Hz IIRC, while the RDAS is configurable up to 200 Hz and uses 10-bit samples. (Those are the ones I'm familiar with.)

10-12 bits at at least a couple of kHz, to make sure the data isn't being garbled by "aliasing" from high-frequency components in the thrust/time curve (as can occur, particularly, with liquid and hybrid motors).

-dave w

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David Weinshenker

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Niall Oswald

David Erbas-White wrote in news:a68Wd.69364$JZ2.533@fed1read02:

I've recently built my own Basic Stamp based altimeter just for the hell of it, and went completely in the other direction:

It only samples about once every second or two, but with the optional board, its 'speaks' the altitude into a cheap and light 500mw 'walkie talkie' style UHF CB radio.

As far as resolution, I ended up deciding that its completely pointless to have a resolution that is greater than the calibration of the instrument. ie: Whats the point of a 1 foot resolution, if its calibration at 3000ft is out by several tens of feet? Thus, because I calibrated this toy at home with a barometer, cardboard box and a vacuum cleaner, I consider the 6 foot resolution that I get to be completely satisfactory. :)

And no, it hasnt flown yet.

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GD

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