How to control the electric current? (for both common material like resin and the special mixed material.)

When coating, the front top pin of the powder coating gun will release high voltages, in general will be about 2-6 ten thousand volts.  Though high voltages, the electric current can be controlled between 10 ua to 100 ua. In general, the raw material of the powder will be resin type, it is without conductive meson, so the raw material will be of good electrification. But if of metal powder (some of the resin material will be with 5% metal powder material), it will be with some electrification, it will be easy with electric charge, so it will have a high performance demand of the powder coating gun, when powder coating, not only well controlled the high voltage, but also outputting low electric current to make a high performance powder coating.