An electronically controlled intravenous infusion set of the gravity feed type having a flow path including a drip chamber and an internal valve for regulating flow through the set. Electromagnetic valve operating structure, positioned outside the IV set, controls the internal valve in response to an electronic control system. The electronic control system serves to open the valve to allow a drop to fall, and includes a control circuit. The control circuit includes an optical drop detector, associated with but positioned outside the drip chamber, which senses the falling drop and signals the control circuit to close the valve. The control circuit also includes a variable frequency clock and associated digital selectors for affording an attendant the ability to precisely select a desired drip rate. An alarm system, operating on digital principles, senses high drop rate or low drop rate conditions and, in response thereto, puts the control system into an alarm condition. The alarm system includes means for digitally adjusting the sensitivity thereof to provide high sensitivity at low drip rates but to decrease the sensitivity at higher rates so that premature alarm conditions are avoided.