Abstract: A flow rate monitor of solid particles or liquid drops and totalizing count display apparatus including a pulsed infrared light source and receiver forming a monitoring beam of high immunity to ambient light, transversely passing through a sensing chamber. A particular application is wherein the system is applied to the drop chamber of an intravenous set having electronic circuitry for pulsing the infrared light source and pulsing the sensing period of the monitoring beam receiver and producing a drop signal for each drop and a visible light flash for each sensed drop. Circuitry responds to the drop signals for maintaining a count of the number of drops and activating a visible numerical display indicating the drop count according to a selected numeric function, and an additional numeric display is provided adjacent the total count display indicating a selected checkpoint number.