1. Conductivity Sensor Seven-electrode conductivity cell
Eliminates proximity effects
The author designed a kind of seven-electrode conductivity cell to sense the conductivity.
The advantage of this design is that this configuration can eliminate proximity effects.
This is four-electrode and the author adds other three electrodes and meanwhile keep the cell axially symmetric.
By the way, there is another parasitic effect called electrode polarization effect. The design that more than two electrodes can removes this effect so four or seven-electrode doesn’t have it.

3. this is current density simulation of seven-electrode
this is current density simulation of seven-electrode. We can see insulating or conducting objects moving around the channel and electrode doesn’t modify the electric field which is generated by the electrodes and is distributed over a relatively large area.