An ionizer (22, 24, 26, 222) comprises: - an alternating current voltage source (V S) having an output outputting a waveform with a positive half-cycle and a negative half-cycle; - an electrode electrically coupled to the output of the AC voltage source (V S); - a ground reference proximate the electrode; -- a shielded cable having a conductor and a shield, the conductor connecting the output to the electrode; and - a sensing circuit including: - a return current nulling node electrically coupled to the ground output of the AC voltage source (V S) and the ground reference, the shield of the shielded cable connecting the ground reference to the return current nulling node; - a ground node separately electrically coupled to ground; - a positive ion current sensor having a positive ion current sense node and being coupled between the return current nulling node and the ground node, the positive ion current sense node being configured to output a positive ion signal proportionate to a sensed positive ion current; and - a negative ion current sensor having a negative ion current sense node and being coupled between the return current nulling node and the ground node, the negative ion current sense node being configured to output a negative ion signal proportionate to a sensed negative ion current, characterized in that the sensing circuit further comprises a balance sensing node coupled between the positive ion current sensor and the negative ion current sensor and a balance sensing sensor coupled between the balance sensing node and the ground node, the balance sensing node being configured to output an ion balance signal proportionate to a balanced ion current, and the ionizer (22, 24, 26, 222) further comprises a feedback control circuit coupled to the balance sensing node, the feedback control circuit being coupled between the AC voltage source (V S) and the electrode, the feedback control circuit being configured to control the AC waveform being applied to the electrode based upon at least the ion balance signal. - an alternating current voltage source (V S) having an output outputting a waveform with a positive half-cycle and a negative half-cycle; - an electrode electrically coupled to the output of the AC voltage source (V S); - a ground reference proximate the electrode; -- a shielded cable having a conductor and a shield, the conductor connecting the output to the electrode; and -- a shielded cable having a conductor and a shield, the conductor connecting the output to the electrode; and - a sensing circuit including: - a return current nulling node electrically coupled to the ground output of the AC voltage source (V S) and the ground reference, the shield of the shielded cable connecting the ground reference to the return current nulling node; - a ground node separately electrically coupled to ground; - a positive ion current sensor having a positive ion current sense node and being coupled between the return current nulling node and the ground node, the positive ion current sense node being configured to output a positive ion signal proportionate to a sensed positive ion current; and - a negative ion current sensor having a negative ion current sense node and being coupled between the return current nulling node and the ground node, the negative ion current sense node being configured to output a negative ion signal proportionate to a sensed negative ion current, - a return current nulling node electrically coupled to the ground output of the AC voltage source (V S) and the ground reference, the shield of the shielded cable connecting the ground reference to the return current nulling node; - a ground node separately electrically coupled to ground; - a positive ion current sensor having a positive ion current sense node and being coupled between the return current nulling node and the ground node, the positive ion current sense node being configured to output a positive ion signal proportionate to a sensed positive ion current; and - a negative ion current sensor having a negative ion current sense node and being coupled between the return current nulling node and the ground node, the negative ion current sense node being configured to output a negative ion signal proportionate to a sensed negative ion current,