Thank you for all suggestions. NMR seem too expensive even if using the proposed inside-out thing. Then there is EMC and power constraints too. I think i=B4ll head for piezoacoustic methods. /Morgan=20 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads