Imho, use a modified air variable capacitor. Remove the rotor bearings and mount it on the manometer, and use a light pigtail wire to connect it electrically (to gnd). The stator will be the hot part and needs to be mounted insulated. Capacitors like this can be read using an AC bridge or a capacitance meter, which is also easy to build into your project. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads