How about the versions of digital vernier callipers that are intended for
use on industrial lathes and milling machines. Most of these have a serial
output and can be connected to a dedicated display or to your own display
device.
They are intended to survive harsh environments and could be hooked up to
constantly touch your beam or be spring loaded against it. They come in
various lengths from 200mm/8inches up to 1m/39inches or so and I am sure
longer ones could be obtained.
Alternatively try a digital DTI (dial test indicator) which has a throw of
about 25mm/1inch and a display and (on mine) a serial output and a ball
bearing on the end of a plunger allowing contact.

Hope this helps,

Simon

-----Original Message-----
From: Madhu Annapragada [mailto:mapr@COMCAST.NET]
Sent: Wednesday, December 03, 2003 6:05 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE:] brainstorming request: measuring small distance in
harsh environment

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