Dynamic modulating voltage adjustment

A continuous inkjet (CIJ) printer comprising an ink droplet generator including an electromechanical transducer, a driver operable to apply a periodic modulating voltage to the transducer to cause a jet of ink ejected by the ink droplet generator to break up into a stream of ink droplets at a breakup time after ejection from the ink droplet generator, and a controller operable to vary a modulating voltage parameter of the modulating voltage and measure corresponding values of a breakup time parameter indicative of the breakup time to obtain a portion of a characteristic of the breakup time parameter against the modulating voltage parameter, wherein the controller is operable to obtain a variation range, to vary the modulating voltage parameter over the variation range to obtain the portion of the characteristic, to calculate a gradient from the portion of the characteristic, to compare the calculated gradient with a predetermined gradient and, if the calculated gradient is less than the predetermined gradient, to generate an adjusted variation range that is displaced relative to the variation range in a first sense, or, if the calculated gradient is greater than the predetermined gradient, to generate an adjusted variation range that is displaced relative to the variation range in a second sense, opposite to the first sense.