Measuring and control apparatus of the corona discharge current

摘要

Apparatus is disclosed in accordance with the teachings of the present invention for obtaining a true measurement of charging current supplied by a corona discharge device to a charge receiving surface. According to the invention, a bridge circuit is formed which includes the corona device as one arm and a first resistor connected in the current return path from the corona device to a power supply as another arm thereof. The remaining arms of the bridge include a capacitor and a resistor connected in series with each other across the source to complete the bridge and provide the signal required to compensate for reactive current through the corona device. The bridge is first brought into balance with the power supply below corona onset voltage, then when the power supply is increased above the corona outset voltage the bridge output potential is used as a feedback signal to maintain the corona current constant. The bridge output may also be used in determining the true corona charging current.