> Is it as simple as it seems....4-20mA current loops....put > across a precision resistor and then feed to the A/D ? Or > better....buffered thru a unity gain amp...? > > Or is it a little more tricky than that? Basically it is just that. You'll probably need a good reference (better than a 7805-suppied Vdd), of course the precision resistor, some protection and filtering against strange things on the input (but the not-too-high precision resistor will help a lot). For realy fancy applications: opto-isolation. 4-20 is often used in a rough environment where power is from 24 or 48 V DC, so you might want to make your input robuust against that, also when applied backwards. Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: www.voti.nl consultancy, development, PICmicro products docent Hogeschool van Utrecht: www.voti.nl/hvu -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist