the flow monitoring device is used with a pump casing on an outflow tube having a passageway therethrough with a wall thereabout . a solenoid pump communicates with the passageway for providing pulsatile liquid flow therethrough . a reduced - in - thickness area along the wall of the casing or outflow tubing has an outside surface establishing a site to measure pulsatile flow along an adjacent inside surface . a thermistor is mounted on the outside surface of the wall area for sensing the temperature thereof in response to pulsatile flow therebeneath . the thermistor is electrically energized at a predetermined level . a control circuit regulates the input of electrical energy to the thermistor for predetermined time periods . the control circuit includes a sample and hold circuit and a reset switching circuit responsive to the pump activation for supplying thermistor power after pumping begins . an amplifier in the control circuit compares differences in the input power to the thermistor during a selected time interval to measure the pulsatile flow rate through the passageway .