Drop counter, photocell, amplifier, and counting down circuit for measurement of blood flow with pen-recorder

A hermetically sealed photoelectric drop impulse pickup has been constructed for measuring the volumetric blood flow in veins and arteries by means of the pen-recorder. A miniature semi-conductor photoresistance is used in this pickup. The wiring circuit of the electron amplifier which controls the pen-recorder is presented. The amplifier allows the internals to be registered either between each drop or after every drop and automatically controls the displacement of the recorder pen at regular intervals. The amplifier also registers the frequency of mechanical impulses (heartbeat, etc.) by means of the pen-recorder.