Air ionizer and method

1. Air ionization apparatus comprising:

a duct including a fan disposed near an inlet thereof for moving air from the inlet toward an outlet;

a pair of ionizing electrodes disposed near the outlet in substantially inward orientations from opposite walls of the duct;

septum electrodes disposed in transverse orientation between walls of the duct near the outlet thereof, and oriented substantially normally to the ionizing electrodes, the septum electrodes including a pair of substantially planar conductive layers spaced apart by a layer of electrical insulation therebetween;

sources of positive and negative ionizing voltages electrically isolated from ground and connected to respective ones of the pair of ionizing electrodes; and

circuits communicating with the septum electrodes for separately sensing currents to ground in the septum electrodes associated with transfers of ions from respective ionizing electrodes.

2. Air ionization apparatus according to claim 1 including a grid electrode disposed over the outlet of the duct and electrically isolated from ground; and

a source of bias voltage connected to supply bias voltage to the grid electrode relative to ground.

3. Air ionization apparatus according to claim 1 in which the circuits include resistors connected between ground and respective ones of the septum electrodes; and

monitoring circuitry connected to sense voltages across the resistors for producing an output representative of a voltage across a resistor attaining a selected level.

4. Air ionization apparatus according to claim 2 including a resistor connecting the source of bias voltage to ground; and

monitoring circuitry connected to sense voltage across the resistor for producing an output indicative of the sensed voltage attaining a selected value.

5. Air ionization apparatus according to claim 3 in which the monitoring circuitry responds to the difference of the sensed voltages attaining a selected value for producing said output.

6. Air ionization apparatus according to claim 4 in which the monitoring circuitry responds to the sensed voltage attaining a selected level relative to ground potential.

7. Air ionization apparatus according to claim 3 in which the monitoring circuitry communicates with at least one of the sources of positive and negative ionizing voltages for altering the level of the ionizing voltage produced thereby in response to said output in a direction toward equalizing the sensed voltages.

8. Air ionization apparatus according to claim 7 in which the monitoring circuitry communicates with the sources of positive and negative ionizing voltages for altering the levels thereof in response to said output in a direction toward equalizing the sensed voltages.

9. Air ionization apparatus according to claim 4 in which the monitoring circuitry communicates with the source of bias voltage to alter the level thereof supplied to the grid electrode in response to said output in a direction toward a selected value.

10. Air ionization apparatus as in claim 1 in which the duct includes an electrically insulated interior wall and includes an electrically conductive grounded exterior.

11. Air ionization apparatus according to claim 1 in which the septum electrodes are substantially aligned in plane-parallel orientation along the direction of air flow from the fan.

12. Air ionization apparatus according to claim 2 including a resistor connecting each septum electrode to ground, and including a resistor connecting the source of bias voltage to ground;

monitoring circuitry connected to receive the voltages appearing across each of the resistors relative to ground, and communicating with the sources of positive and negative ionizing voltage and with the source of bias voltage for altering the levels of at least one of the positive and negative ionizing voltages, and for altering the level of bias voltage in directions to provide substantially balanced levels of positive and negative ions flowing through the grid electrode in a flow of air from the fan.

13. A method of producing controlled amounts of positive and negative air ions in an air stream, the method comprising:

forming positive air ions and negative air ions in electrically isolated separate portions of the air stream;

sensing rates of production of positive and negative ions in the air stream;

altering the rate of production of at least one of the positive and negative air ions in response to the sensed rate of air ion production of the at least one thereof relative to a selected rate;

sensing the positive and negative ions flowing in the air stream; and

electrostatically altering the flow of positive and negative ions in the air stream toward substantial equality in response to the sensed air ions flowing in the air stream.

14. The method according to claim 13 in which the positive and negative air ions are formed in regions of the air stream in response to ionizing voltages supplied between ionizing electrodes and electrically separated, substantially planar electrodes that are aligned along the air stream, the method comprising:

sensing ion current flowing in each of the planar electrodes; and

altering at least one of the ionizing voltages to alter the rate of production of ions therefrom in a direction toward equalized production rates.

15. The method according to claim 13 in which ions in the air stream flow through an electrically conductive grid; and the method includes altering voltage on the conductive grid to electrostatically alter the flow of positive and negative ions flowing therethrough.