Unable to get this to properly plot analogue input values

[BNNorman]

Really excited when I found this, so much potential. Examples work fine but I cannot get a clean line plotting the analog inputs of my NANO.

The display I get clearly shows the voltages on the analogue pin, and the correct ranges, but I can't get a clean line. See attachments showing Listener.exe (Windows 10 64bit PC) window before and after auto scaling. I have changed the points to plot (500,1000,5000) - it just changes the refresh rate not the plotted line. I have tried adding delays in the loop - only the refresh rate changes..

Your examples work fine but I noticed they seem to use a 'timebase' of 5000 for their calculations. My analog input won't change rapidly - more likely to vary over a number of seconds, minutes or hours though quick reads in succession should give the same value resulting in a horizontal line.

What can I do to solve this

#include <Plotter.h>

float Vout;  // Analogue voltage
Plotter p;

#define SIG A4
#define CONTROL 10

void setup() {

  pinMode(CONTROL,OUTPUT);
  digitalWrite(CONTROL,HIGH);

  // now start the plotter

  p.Begin();

  p.AddTimeGraph( "Ion Chamber Vout", 5000, "Vout", Vout);
}

void loop() 
{
  Vout=5.0*analogRead(SIG)/1023.0;
  p.Plot();
}

[BNNorman]

After some playing around with the loop this started to make sense:-

uint32_t Step=0;

void loop() 
{
  Step++;
  if (Step==100)
    {
    Vout=5.0*analogRead(SIG)/1023.0;
    Step=0;
    }

 p.Plot();
}

However, as you can see from the attached auto adjusted plot it gets difficult to interpret without vertical lines.

![plotter slowed down](https://user-images.githubusercontent.com/15849181/49516658-05249f80-f892-11e8-9044-4abe9fcd7981.JPG)
![plotter slowed down 2](https://user-images.githubusercontent.com/15849181/49516699-21c0d780-f892-11e8-99eb-bcfc10216a39.JPG)

[devinaconley]

@BNNorman - based on that pattern I would guess that a float value is being multiplied against an int, resulting in lost precision between "steps".

I believe that analogRead returns an int... try casting that to a float value before multiplying against 5.0

[BNNorman]

Thanks for the reply. It was my understanding that the compiler would treat the entire calculation as float if any of the numbers were float. I'll give it a try tomorrow and let you know. I've tried putting a cap on vref and the analog in but no change so not sure if hdw or sw. But, i have to say that an int less than 1024 divided by 1024 would yield zero in integer math and thats not what i am getting.

[BNNorman]

The noise is in my electronics. If I tie a NANO ADC input to 3.3v it's almost rock steady. The circuit comprises of an Ionisation Chamber and a chip (RE46C112) designed to monitor the chamber voltage hence smoke/dust. I guess I need to add some more smoothing capacitors.