Abstract: In large size high resolution plasma panels, a smaller discharge gap between the electrodes reduces the operating margin of the panel, i.e., the difference between the maximum and minimum sustain voltage (V.sub.s max and V.sub.s min). Rather than preset these values which vary with each panel at the time of fabrication, the invention provides a control system for determining the V.sub.s max and V.sub.s min and the optimum operating point between these values for each panel. An associated microprocessor determines the V.sub.s min for each panel through a testing algorithm, and the V.sub.s max is provided by either adding a predetermined increment to the V.sub.s min or by a testing sequence. The operating point is designated as a predetermined increment below V.sub.s max. The invention operates each time the panel is turned on, thereby compensating for voltage drift or other panel parameter variations.