What is the fringe field effect?

The fringe field effect occurs in four ring EC probes.

Fringe Field Effect is when the measurement field, the constant electrical current, extends outside of the probe. You only need to worry about the fringe field effect if your probe is too close to the sides of the container or pipe where you are taking an EC measurement. A good rule of thumb is to keep the probe at least an inch away from all surfaces. The distance you need to keep the probe varies, so just check the manual.