Importance

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Abstract

Ion content of the air in a clean room or the like is controlled by generating positive and negative ions during alternating time periods using positive and negative high voltage generators connected to ionizing electrodes. Ion generation periods are followed by off intervals during which the ions disperse away from the electrodes before ions of opposite polarity are generated. In one aspect of the invention, each period of actuation of a high voltage generator of one polarity is followed by a momentary actuation of the high voltage generator of opposite polarity. This produces ions that are attracted to the electrode of the one polarity and then neutralize residual charge on the capacitors of the generator of the one polarity thereby assuring an abrupt termination of ion generation which can otherwise extend into the subsequent off period. In another aspect of the invention, each ion generation period is interrupted for an interval which varies in accordance with a feedback signal from an ion sensor in order to maintain air ion content within a desired range. The feedback signal is integrated to suppress the effects of brief localized fluctuations of air ion content on the signal thereby avoiding unnecessary over production of ions.

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First Claim