On Friday, December 30, 2016 at 7:02:00 PM UTC-5, Jim Wilkins wrote:
wrote in message
...
On Friday, December 30, 2016 at 3:16:34 PM UTC-5, Clare wrote:
On 30 Dec 2016 03:33:36 GMT, "DoN. Nichols"

wrote:

On 2016-12-29, Jon Elson wrote:
wrote:

So I was looking at some rotary encoders and a thought occurred
to me
that maybe I could make a level with a digital display for
checking
lathe bed twist. The highest number of pulses per revolution
available
was 40,000. That works out to only .009 degrees. Seems pretty
small
huh? But .009 degrees is 36 seconds! That works out to .0016" in
10
inches. My fairly inexpensive precision level shows .0005" in
ten
inches. That's ten seconds resolution. And I know it's accurate
'cause I checked it with gauge blocks. I know, overkill, a
feeler
gauge would be good enough. I guess I'll stick with the level
and just
watch the analog bubble display.
Eric
Lucas made some liquid inclinometers that had a resistive liquid
inside and
some traces on a PC board that turned it into essentially a
potentiometer
with a plumb weight. Kind of worked. No friction, which is what
would make
the mechanical version (weight and encoder) not work very well.

I've seen similar devices, a small metal dome with about the
curvature of a golf ball (without the dents) which has four
electrical
contacts in a Bakelite insert, and a connection to the metal dome
itself. The liquid was likely something like a saline solution,
selected to not attack the electrodes or the dome. (Both appeared
to be
either silver or silver plated.

The original used mercury

I remember hearing that not having a level is easy too. Just tie a
bolt onto string and hang it from the ceiling. There you have what is
called a plum bob. Its shadow (from the ceiling on down) is an exactly
verticle line down, so its right angle is an exactly horizontal one.

=================================

A plum(b) bob won't help in an airplane because "down" during a turn
isn't really vertical, and if you think it is your time will be brief.
https://en.wikipedia.org/wiki/Graveyard_spiral

Large warships needed a complex instrument called the Stable Vertical
to tell the gunnery computer which way is up.
http://www.navweaps.com/index_tech/tech-074.htm
It explains the mercury.

-jsw

"A plum(b) bob won't help in an airplane...."
Unless you're fueling it with the tanks' dripsticks. There's one in the main gear wheelwell on the keel beam.

Garrett