I know for a fact that Banner and Turk both make Inductive proximity sensors
that can be used in harsh environments (both mechanical and electrical). Now
the problem is that these sensors would give you a yes or no answer to the
presence of metal very accurately but how are you going to measure distance
from that? Fixed distance sensing is one thing but if you want to sense
metal that can vary in distance from the sensor, you will need an analog
output that is fairly linear in your measurement range; you might try
talking to applications engineers at Turk, Keyence and Banner. Between them
I am sure they will recommend a good solution albeit an expensive one.
Madhu

>-----Original Message-----
>From: pic microcontroller discussion list
>[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Alvaro Deibe Diaz
>
>I think ready-made industrial inductive sensors can be a good solution, if
>you can decouple from the electric noise surrounding the sensor.
>
>Another possibility could be an ultrasonic sensor. Very precise, quick and
>inmune to EE noise, paint and grime. A little expensive approach, though.
>

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