Sorry for the delay, things have suddenly got a bit hectic here. On Sun, Apr 10, 2011 at 2:37 AM, Harold Hallikainen wrote: > I don't see any reason to have the op amp between the divider and the ADC= .. > If the 0-10V source can drive a 20k load, I'd just have your 10k/10k > voltage divider directly drive the PIC input pin. I'd use resistor > networks for the resistors to try to get the temperature coefficients to > match and the temperatures to match. Most PIC ADCs can take a 5k source > impedance with full accuracy (your 10k/10k voltage divider would have a 5= k > Thevenin resistance (assuming a 0 ohm resistance for the 0-10V source). Ok, that makes sense. > If you're measuring a bunch of pots, it'd be nice to drive the pots with > the same 5V source as the ADC reference. Then you don't have errors from > the voltage divider or mismatch between the pot voltage source and the AD= C > reference. I think I'm going to redefine what I want out of these boards. Originally my plan was to have the inputs able to take a voltage divider (ie to read a pot) as well as accept an external 0-10V input signal. I've read pots before, but I wanted to add another layer in case someone decided to feed something funky into the external input. I'm now thinking it might be smarter to make a board to fill my immediate need (reading pots), then if I ever actually need to use external inputs, add a small buffer/protection board when the need arises. I like the idea of using resistor networks, I think I will use that. I'll make sure I lay everything out so that I can jumper straight past them if I am able to use a +5V source on the pots. Thanks! Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. =A0 =A0 =A0 =A0 -Douglas Adams --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .