The problem you are experiencing is due to the sample and hold of of the ADC input which is multiplexed to all analog inputs. If you don’t use a low impedance source, you will see bleed through from one ADC channel to the next. What you need is a opamp connected between the circuits you are measuring and the ADC input. The opamp will provide a low impedance source for the sample and hole (S&H) and prevent the bleed through from one channel to the next.
Regards, John > On Jan 18, 2018, at 7:34 PM, mateuslucas.l7...@gmail.com wrote: > > > > > > > I'm using two analog inputs, the first with a LDR and a resistor of 10k Ohm, > connected at P9_39 (AIN0), and the second connected at P9_38 (AIN3). > When the lights are down, the measure of LM35 works very well, with a low > distorction, +/- 0.2 ºC. > But when the lights are on, the measure of LM35 starts to float, about +/- 1 > ºC. > I have tried to put a 4.7nF between GNDA_ADC and AIN3, but the distorction > continues. > > I asking for help to diminish this distorction when the lights are on. > > > -- > For more options, visit http://beagleboard.org/discuss > <http://beagleboard.org/discuss> > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to beagleboard+unsubscr...@googlegroups.com > <mailto:beagleboard+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/d5353977-2025-4aa3-b6a0-361742ae9c96%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/d5353977-2025-4aa3-b6a0-361742ae9c96%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/F6484468-7890-40D1-94C4-F7850E711059%40gmail.com. For more options, visit https://groups.google.com/d/optout.
