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. Alvaro Deibe. > How about a small inductive sensor, a reference coil of the > same inductance with an oscillator and an instrumentation > amp? - Confused? - OK see the attachment. The reference coil > should be subjected to the same EMP as the sensor and cancel > out the noise. Never actually tried it, but worth a shot. > If you do get interference, use a band pass filter tuned to > your oscillator. > > Brian. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads