Which side is the ionizer and which is the collection plate on a whole house air cleaner?

I took the filters out of the 2 whole house air cleaners to 2 hvac units so I could clean them and then couldn't remember which one went to which. The air first passes through the prefilter screens, then the ionizer and then the collection plate. Does anyone know if the collection plate is the side that looks like louvers or the tighter looking side? If it helps any, they are Trion HE 2000 plus electronic air cleaners.