Abstract: A portable ultrasonic diagnostic instrument including an array transducer, a beamformer, signal processing and imaging circuitry, and a display for the processed echo signals operates on no more than 25 watts of electrical power. Circuit functions can be selecting attend depending on mode of operation of the instrument to thereby reduce power consumption. Further, a power monitor and control can monitor electrical current from a battery power source, and when power consumption reaches a pre-determined level the power monitor and control further alters one or more functional units in the instrument including display mode of operation, clock frequency for analog to digital conversion and signal processing, color signal processing, and 3D signal processing. Power consumption can be monitored against two or more pre-determined levels wherein instrument functional units or mode of operation are altered depending on which level of power consumption has been reached.