In all that EM noise, I would suggest a Stanley Tape Measure. Cheap, reliable, highly noise immune, and accurate to 1/16". Plus, it snaps back into the case on a spring, real handy, and has a clip for your belt. Seriously, optics and ultrasonics are going to be your best choice, and you'll have to go full-on industrial stuff with lots of shielding, not cheap, to compete with so much electrical noise. Good luck even then. Plan to put the whole thing in rigid metal conduit, seriously. -- Lawrence Lile Alvaro Deibe Diaz Sent by: pic microcontroller discussion list 12/03/2003 10:22 AM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: Subject: Re: ] brainstorming request: measuring small distance in harsh environement 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 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads