Interference in the ADC

[roman_arduino]

Hi all! I am using an arduino nano with an atmega328p for voltage readouts (ADC). I have very large interference (change in the ADC value by 40 values), although I measured it on an accurate voltmeter, everything is in order with the voltage (it is stable). What could be wrong? I use an ADC measurement with a range of 0 - 1.1V (0...1024).

[horace]

upload a schematic showing the wiring? show the analogue and digital grounds and how you power the system
upload the program (using code tags </>)

[johnerrington]

If you want reasonably reliable results you may find it useful to read this:

skillbank: Experiments and projects with an Arduino microcontroller

@roman_arduino

What could be wrong?

If your circuit has anything more than this

then other components may be introducing noise.

So the first step would be to disconnect everything except the supply and the voltage source.
And the next step would be to look at the voltage input AND the supply voltage with an oscilloscope. A DVM will not tell you if a voltage is stable.

Please provide the basics - a schematic, a photo and your code.

How to make a schematic you can post.

When you submit a question on the forum you will usually need to add a schematic (circuit diagram). The tutorial that follows will explain some ways to create a useful image; however lets start by explaining how to add the image to your post. Its easy. Having created the image all you need to do is : Save the image somewhere convenient - maybe your desktop Start your post, and place the cursor (insertion point) where you want the image to be shown; [upload image to forum] 3: click th…

[awneil]

@roman_arduino

very large interference (change in the ADC value by 40 values)

It's a 10-bit ADC, so you're seeing changes of 40 over a range of 1024 - that's under 4%.

@roman_arduino

I measured it on an accurate voltmeter, everything is in order with the voltage (it is stable)

A voltmeter will average over a (relatively) "long" time - so it probably won't see noise that the ADC does see.

Try averaging your ADC samples over a similar time...

[GolamMostafa]

@awneil

It's a 10-bit ADC, so you're seeing changes of 40 over a range of 1024 - that's under 4%.

OP's Full Scale: 1.1V
Resolution: 1.1V/1024 = 1.07 mV
ADC Error: +/- 2 LSB ==> 2.14 mV
So, a reading must flactuare within n+/-3.

[GolamMostafa]

Try putting 0.1uF capacitor at the input of the ADC channel. Also, include the following line in the setup() finction.

analogReference(INTERNAL);

Please, post your sketch.