Method and apparatus for controlling a multi-nozzle ink jet printhead

A multi-nozzle ink jet print head having a plurality of nozzles divided into more than one group of nozzles with each group of nozzles having more than one nozzle;

• a pressure modulator for causing streams of ink emitted from the nozzles to be broken up into individual droplets;
• more than one group of charge electrodes, each group of charge electrodes having a respective charge controller been positioned for each group of nozzles to supply a charge signal waveform to each charge electrode in turn;
• means for generating a pressure modulation waveform applied to said pressure modulator;
• means for adjusting the phase of the charge signal waveform relative to the modulation waveform;
• means for determining the optimum phase relationship to achieve proper charging for each droplet stream;
• and
• said means for adjusting the phase of the charge signal waveform relative to the modulation waveform operating to independently for each group of charge electrodes:
• operating the respective charge controller to supply a charge signal waveform to each charge electrode in turn;
• adjusting the phase of the charge signal waveform relative to the modulation waveform between 0 and 360 degrees in a number of steps;
• determining the optimum phase relationship to achieve proper charging for each droplet stream in turn;
• and thereafter adjusting the phase of the charge signal waveform relative to the modulation waveform to achieve charging of droplets in all the streams in the group simultaneously.