I'm currently working on the Python software to interface with the EC/pH/Control board and also developing the web interface.
For testing, the spray cycles are running every minute. As you can see in the second picture, everything is sitting on my desk, so it's only running simulated spray cycles.
The approximately linear increase in conductivity over time is due to water evaporation. Since only pure water evaporates, the density of the dissolved ions left in solution increases, and that increases the conductivity.
I've made an EC calibration setup with solutions of various conductivities in cups that are hot melt glued to a base, in order to avoid spills. The pH probe is sitting in a standard pH 4 probe storage solution. The plot above shows that the pH is slightly temperature sensitive. A thermistor built in to the EC probe measures the temperature. The solutions are stabilizing to the same slowly changing room temperature.