From: default@defaulter.net   
      
   On Thu, 12 Jun 2008 22:13:36 -0700, GeoSound    
   wrote:   
      
   >400,000 digitized steps in an A/D!   
   >Accuracy to measure down to the centimeter!   
   >Don't need someone else to do it just if my thinking is reasonable!   
   >Education is a curse   
      
   You can do whatever you want - if you want a degree resolved into a   
   million steps you just have to figure out how to do it.   
      
   Check out LVDT's Linear Voltage Displacement Transducers (or something   
   close to that) it is a whole science of precise small distance   
   measurement - and lots of off the shelf solutions.  The stuff is   
   relatively easy to build too once you know the theory.   
      
   Another cheap and dirty idea is to use an optical potentiometer - a   
   diffused light source opposite a diffused light detector (photo   
   resistive element) in between the two is a mask with a long triangular   
   cutout.  As the cutout moves from one extreme of its range to the   
   other, it varies the amount of light allowed to pass from emitter to   
   detector.  Typical photo resistor might be 10 ohms in bright light and   
   5 meg ohms in darkness.   
      
   Want to get really fancy?  a small laser - moving mirror - beam   
   splitter and you can resolve down into the nanometer range with   
   constructive and destructive interference.   
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