Abstract: A flow controller is provided that detects intervals between successive drops and responds to detection of intervals which are too long by shutting down operation of the administration set if the abnormal flow causing the long interval cannot be corrected. In response to detection of abnormal flow which is not clearly a high flow condition and/or an empty container, the flow controller sequentially opens, closes, re-opens and again closes the clamp of the controller in an attempt to restore normal flow. If normal flow is restarted before the sequence is completed, the controller returns to normal control of the fluid flow. Otherwise, completion of the sequence results in a shutdown of the system and activation of an alarm. In keeping with the invention, indicia are provided in connection with the drop chambers of the administration sets which are sensed by sensing means mounted to the drop detector of the flow controller in order to indicate to the controller the size of the orifice in the drop chamber.

Abstract: An intravenous monitoring system in which dynamic reference threshold circuitry is used to provide output signals indicating the presence of liquid passing through the drip chamber of an intravenous feeding apparatus. A light sensor that detects the presence of liquid passing through the drip chamber generates a detecting signal that is amplified and processed by the dynamic reference threshold circuitry. The dynamic reference threshold circuitry comprises a comparator circuit, and a D.C. component reference circuit that provides the reference threshold to the comparator circuit. The amplified detecting signal is directed both to an input of the comparator circuit and the D.C. component reference circuit. The D.C. component reference circuit uses a diode to produce a voltage drop in the amplified detecting signal and an RC circuit to both store and emit a residual signal when there is a sudden drop in the amplified detecting signal.