Certainly worth narrowing down equipment coming on/off since close electrical signals could be causing interference.Hmm, another result that suggests the issue is local to me. I will have to look for a local cause. Though as time goes on, it seems like the instability is decreasing. I also noticed that it took about 2 weeks for the constant creep higher in readings to moderate.
I also may be mistaking sensitivity for instability. I read the probes every 5 minutes and I noticed that when I get a jump of +/-100 uS from the previous reading, it seems to affect all the probes equally.
Hmm, more testing needed.
I’m reading the EC probe at 3 decimal places every 5 minutes and the graph is a straight line. No variation except for when I top off.