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A minicomputer-controlled system is used to automatically measure the wall charge transfer curve of a single cell in an ac plasma display panel. Curves can be plotted on a graphics display as fast as 5/s which allows real-time interaction with the user. The measurement technique is based on the ability to directly measure the wall charge from a single cell. The minicomputer controls the sustain voltage across the cell and obtains the resulting wall charge. It then does the tedious algebra needed to complete the transfer curve. The measured curves show numerous interesting effects. The influence of the state of the neighboring cells can clearly be seen. The duty factor of the sustain waveform has a strong influence on the transfer curve. An effect dependent on sustain frequency is presented that shows a transfer curve region with negative slope. The most interesting effect measured is a hysteresis in the transfer curve, in that a different curve is traced out as the cell goes from off to on than when it goes from on to off.