Abstract: An improved system for determining the optimal phase time to charge a liquid stream emitted from a jet as it evolves in form from a continuum to a separatuum of droplets wherein the optimal time for achieving the desired level of charge on a given droplet may be had by applying the charge immediately prior to break-off of droplets. A particular use of the system is in an ink jet droplet apparatus having a controlled liquid stream of ink that is separated into droplets by a sonic transducer and then charged by a pair of charging plates in a dynamically controlled manner at an optimal phase time as correctably tested by the system for subsequent static deflection of the charged droplets to a desired portion of a document to form printed characters.