On Thu, Jan 29, 2015 at 5:19 AM, wrote: > Were all the unit external inputs and outputs connected and operating at > full currents and cable lengths? Yup. > I would work on a suspect unit and turn the pot to minimum (0v rail) - > any noise then should not be due to the power supply but could be series > mode noise - probably due to digital circuit currents in the ground > track between the ADC 0v pin and the pot low end. Interesting. I will try that next time I get to touch one of the troublesome units. I'll run a jumper temporarily and see how that goes. > Obviously if the noise increases as you turn the pot to the 5 volt end > then the supply rail is likely to be the source - again probably due to > digital spikes. As I recall, the two extremes were pretty rock solid. Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .