Voltage divider for 6 non intrusive current sensors
I assume you refer to a circuit like this:







simulate this circuit &ndash; Schematic created using CircuitLab

The "reference" you speak of is not a reference - it is a virtual ground. A ground reference that is at a different potential to the Arduino - in this case 2.5V higher.

Since it is just the ground for the circuit you can use the same one for all the current transformers without problems.

If the offset voltage were applied to the output (as is often done for active devices that create an AC waveform, such as audio signals) then you would require a separate offset voltage for each one, since otherwise you would be connecting all the outputs together, which would be bad.

You can also "reverse" your thinking. The "offset" voltage you apply is ground, and the Arduino's "ground" is 2.5V below that. It's all relative.