A method of operating a continuous liquid drop emission apparatus includes providing a liquid drop emitter that emits a plurality of continuous streams of liquid through a plurality of nozzles. A jet stimulation apparatus transfers energy to the liquid sufficient to cause the break-off of the plurality of continuous streams of liquid at a plurality of predetermined break-off times into a plurality of streams of drops of predetermined volumes. Sensing apparatus measures a characteristic value for each of the plurality of streams of drops of predetermined volumes. Control apparatus provides a plurality of break-off time setting signals to the jet stimulation apparatus to cause the plurality of predetermined break-off times to be determined by the characteristic value of each of the plurality of streams of drops of predetermined volumes.