Ohmic heater with multiple operating states

A method of heating a liquid, the method comprising:

• passing the liquid in a downstream direction between a first pair of electrodes disposed adjacent one another in the downstream direction but spaced from one another in a direction perpendicular to the downstream direction, then through an elongated passage defined by a dielectric wall and then through a second set of electrodes disposed adjacent one another in the downstream direction but spaced apart from one another in a direction perpendicular to the downstream direction;
• actuating an electrical circuit to apply a voltage, the electrical circuit operative in at least three states, the at least three states comprising:
• a first state in which the electrical circuit applies a voltage between the electrodes of the first pair,
• a second state in which the electrical circuit applies a voltage between the electrodes of the second pair, and
• a third state in which the electrical circuit applies a voltage between at least one electrode of the first pair and at least one electrode of the second pair so that in the third state, in which the only current path through any of the electrodes extends between an electrode of the second pair and an electrode of the first pair, through the elongated passage, and current flows through the liquid in the elongated passage, wherein in the third state, the only current path through any of the electrodes traverses the electrode of the second pair and the electrode of the first pair and does not traverse any electrode other than the electrode of the second pair and the electrode of the first pair;
• detecting at least one condition of the liquid, the electrical circuit, or both;
• and
• controlling the electrical circuit to select the first, second or third state responsive to detection of the at least one condition.