With only two SMU channels, you will have to move cables for each step of the VDP measurement.
But for each step, one SMU forces current and other SMU forces 0A and measures V.
Is easier if you have 4 SMU channels, one for each contact point in the VDP test structure.
As needed for each step, each SMU can be current source, LO return or voltage measure, so no need to move cables.
