Hello,
I use a Tripp Lite isolation trans my self and can tell you that it is not truly isolated in the fact that on the secondary side the neutral is also connected to the chassis. This is however easily corrected by opening up the unit and you will see that on one side the white neutral wire has a green wire spliced to it and is connected to a chassis ground stud. simply remove the green wire from that stud and insulate it with heat shrink and now you will be fully isolated from ground on the output.
This helps keep the sphincter pucker factor down when working on sketchy equipment.