EC readings from Atlas sensor are erratic

Hi Kyle, first off thanks for your great work making your YT video and build article for the hydropnic system, and of course for developing mycodo.

I have my system up and running everything was going pretty well until I started getting erratic EC measurements which is throwing off my abilities to control the state of the nutrient solution. I am seeing measurements like the following, with a few at what I think is the correct level, then a single measurement far lower, then returning to the normal level. I have a feeling this might be an issue well known to those more experienced, so i thought i’d throw it up here to see if there was an immediately obvious cause of this sort of thing.

For now I have turned off the pH sensor data collection and things seem to be improved but I will need to get them working together so any hints would be appreciated.


I think I have “sorted” this, but i don’t know how. All I did was turn off the pH sensor for a while, found that the EC sensor was working much better without it turned on, and the turned it on again to find much more stable results. Its always a little worrying if you don’t understand the cause of something, but for now I will settle for things having settled down a bit…

Now onto the strange messages being generated by the Atlas pH and EC inputs in the mycodo logs… No doubt that has been explored elsewhere.

My understand is that these sensors need to be electrically isolated as their readings can affect each other. Perhaps yours are, just thought I’d mention it.

Agreed. It should be assumed there is interference occurring to some degree and testing should be performed to discover the source. This is typically isolating each water-sensing device, removing all other sensors or possible sourced of interference (water pumps, float sensors, etc.) so you have an electrically-isolated body of water with only a single sensor probe in it. From there, introduce your new variables (sensors, pumps, etc.) to find what is the source of the issue.

Darn - the pump interference is a good point, I was going to put my sensors inline with the pump using these doodads. Now it occurs to me that might cause interference. Maybe I’ll use your approach and have the water pour into a separate container and place the probes there.

That in-line pipe sensor mount should be fine, especially if you’re using Atlas Scientific sensors, since they are good about electrically-isolating their circuits. Even though I have a second reservoir for my sensors, the water still completes a circuit with the pump, but it has no effect on measurements. The second reservoir is primarily to ensure the sensors stay hydrated (most important for the pH sensor to always be submerged), since the rise and fall of water level in the main reservoir has no effect on the water level in the second reservoir.

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