Gen III and DFPM Cadenc

[turbomentor]

I'm getting ready to install a PT along with my iAero GIII for some comparison rides.

Looking at the installation instructions, it says not to use the iAero cadence sensor because the DFPM is supplying cadence. However on the PT there is no cadence sensor and I remember (vaguely) cadence is "virtual" whatever that means. The question is can I choose to use the iBikes cadence sensor or am I stuck with using the PT cadence data? I prefer having magnet measured cadence!

Thanks