[simpits-tech] Zero point on a two needle altimeter

[Craig Rochester]

Dumb questions about altimeters, speed indicators, etc. If they work like
this: http://home.swipnet.se/~w-65189/AP_html/pitot_static.htm why can't you
just output two pressures?  The velocity pressure could be controlled by a
voltage driven pressure regulator(V/P) and compressed air.  The barometric
pressure would require vacuum and a vacuum version of a V/P.

This way you could use standard instruments without modification.

Craig R.

-----Original Message-----
From:	simpits-tech-admin@simpits.org [mailto:simpits-tech-admin@simpits.org]
On Behalf Of Matt Bailey
Sent:	Saturday, October 26, 2002 7:35 PM
To:	simpits-tech@simpits.org
Subject:	Re: [simpits-tech] Zero point on a two needle altimeter

Heh, good idea. But how do you tell where the needles are? Unless you
put a sensor on the hour hand, which would give you 100,000feet (like I
mentioned before), assuming the clock had all three hands. Are you using
the clock idea in your F-15?

	-Matt Bailey

Gene Buckle wrote:
>
> You guys are missing the obvious.  Buy a cheap battery powered clock drive
> and drop the original motor out of it and drive it with a stepper motor.
>
> g.
>
> On Sat, 26 Oct 2002, Matt Bailey wrote:
>
> > Interesting ideas on this subject! One thing to keep in mind, the
> > relationship of the turning of the hands of an altimeter is always the
> > same, the hundreds needle always makes 10 revolutions per one revolution
> > of the thousands needle etc. So you really only need one connection to
> > the motor and sensor (perhaps on the hundreds needle, for precision) and
> > just drive the other needles off that, using gears or pulleys. Also, if
> > you had a way to measure the position of the ten thousands needle, your
> > software would always know where that needle was and hence where the
> > other needles are...only problem might be resolution since there is so
> > much difference between this needle and the hundreds needle, for
> > instance. But without having to count the number of revolutions for this
> > needle, you would get a range of 100,000 feet. Quite sufficient for
> > anything other than very high performance fighters (like the F-104) or
> > spacecraft.
> >
> >       -Matt Bailey
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Thanks!