Patent ID: 7249830

Claim:
A method for controlling the jet break-off length in a liquid drop emitter apparatus containing a positively pressurized liquid in flow communication with a plurality of nozzles and comprising resistive heater apparatus adapted to transfer pulses of thermal energy to the liquid sufficient to cause the break-off of the plurality of continuous streams of liquid into a plurality of streams of drops of predetermined volumes, sensing apparatus adapted to detect at least one stream of drops of predetermined volumes, and control apparatus adapted to calculate a characteristic of the at least one stream of drops and to provide a break-off length calibration signal to the resistive heater apparatus, said break-off length calibration signal determined at least by the characteristic, the method for controlling comprising: (a) selecting a break-off test sequence of electrical pulses; (b) applying the break-off test sequence to the resistive heater apparatus thereby causing at least one stream of drops of predetermined volume to break-off at a test break-off length; (c) detecting the arrival times of the drops of the at least one stream of drops of predetermined volume; (d) calculating a characteristic of the at least one stream of drops of predetermined volume; (e) providing a break-off length calibration signal determined at least by the calculated characteristic to the resistive heater apparatus, said break-off length calibration signal determining an operating sequence of electrical pulses; and (f) applying the operating sequence of electrical pulses to the resistive heater apparatus thereby causing at least one stream of drops of predetermined volume to break-off at an operating break-off length.