A method and assembly varies the image density of ink from a plurality of ink jet nozzles to provide substantially uniform ink density. Electronically and automatically the electrical power consumption of an ink jet device having an electrical heater is measured (typically by measuring the current draw), and in response to that measurement, if necessary, pulse or voltage supplied to the heater or heaters of each of the ink jet devices is automatically adjusted. More electrical power is supplied if greater image density is required for a particular ink jet device, and less electrical power if lower image density is desired. During typical operation all pulse widths are reset to default settings, the signal received is calibrated, a pattern generator is signalled to provided test data, the present peak electrical current consumed by each nozzle heater is sampled, and the pulse width for each nozzle heater is set based upon the current sample.