I have an extremely high quality pH electrode hooked up to an Arduino MEGA that we're using for a product we're making.
Now everything looks good. The voltage is stable as hell over extremely long times when checked.
However, on the Arduino end analogRead shows a curious trend. The values seem to oscillate quite a bit (close to 1 pH in difference, which is obviously intolerable from a sensor that should do 0.01pH).
Here's an image showing what I'm talking about: (oh sorry apparently not, as I need to post a regular message before I'm allowed to post one with a link.. see the first response to this post for a link to the image) The phenomena is best seen in the (unnamed) Sample 6.
What's truly bizarre is how long the oscillation is. From peak to peak is close to 1 MINUTE, which is highly problematic as it makes smoothing pretty much useless - we can't possibly have a machine that needs a sample size of 5 minutes or more to be properly smoothed.
Any idea what might be causing this?