Capacitive sensors work by measuring the changes in capacitance when more or less of the fluid is in proximity of the sensor. They are often designed as strips or bars that go down in the fluid measured, and will detect how far up the sensor the fluid reaches.
Some capacitive sensors can be mounted on the outside of the tank, but that requires a non conducting container. Capacitive sensors also require that the fluid is conductive.
Conductive sensors can be very rugged and provide good accuracy and little drift over time. The output is typically analog, such as 0-10V or 4-20mA, and will match the inputs on the ezeio system perfectly.