Abstract: Ion content of the atmosphere at a particular location is controlled by generating ions during repetitive period that are initiated by timing signals which reoccur at a predetermined rate. An ion sensor produces feedback signals indicative of the ion content of the air and a feedback circuit varies the duration of the recurring periods of ion generation, if necessary, to maintain the ion content within a predetermined range. Positive and negative ions may be generated during alternate ones of the repetitive periods in which case the feedback circuit inversely varies the periods of positive and negative ion generation to maintain the relative proportions of the two types of ion within a predetermined range. The method and apparatus may be used to suppress accumulation of electrostatic charge by objects, such as in a clean room where electronic components are manufactured, or for other purposes requiring control of the ion content of air.

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.

Abstract: Apparatus for ionizing air molecules to suppress electrostatic charges in a room or for other purposes includes internal feedback which maintains a desired rate of ion production in the presence of electrode deterioration or other effects which could otherwise alter ion output. Production of air ions of a given polarity results in a ground return flow of electrical charges of opposite polarity from the high voltage generator at a rate corresponding to the rate of air ion output. The ground return current is monitored to produce an electrical feedback signal. A control circuit causes the high voltage generator to apply higher voltage to the electrode when the feedback signal decreases and to apply lower voltage to the electrode when the feedback signal increases. Such self-regulation of each individual electrode in systems having an array of electrodes that are otherwise jointly controlled acts to maintain a desired ratio of positive and negative ions in a room as well as a desired total ion concentration.

Abstract: Positive and negative ion contents of the air within a region are controlled to suppress build-up of electrostatic charges on objects or for other purposes with one or more air ionizing units each having a positive high voltage generator coupled to a first ionizing electrode and a negative high voltage generator coupled to a second spaced apart ionizing electrode. The positive and negative high voltage generators are operated alternately with off times being provided between each period of ion generation of either polarity and the preceding period of generation of ions of the opposite polarity. The off times enable ions of each polarity to disperse outwardly for a controlled distance before substantial intermixing and mutual neutralization takes place.