3609379 is referenced by 49 patents and cites 5 patents.

This disclosure is of a fluid flow rate control for intravenous feed and like applications wherein flow occurs in dropwise fashion. Drops are sensed photoelectrically by interruption of a light beam incident upon a photocell, the resulting fluctuations in output of the cell being detected and utilized for closed loop control of a flow adjustment device operative to correct any drop timing error detected. The control circuitry described includes means enabling discrimination between discrete drops and a steady stream or column of liquid as occasionally is experienced in intravenous feed apparatus, and means enabling discrimination also as between the primary or main drop and small secondary drops which sometimes form with and trail immediately after the main drop and which, if sensed, introduce errors into the drop timing measure obtained. For purposes of shutting off flow just prior to exhaustion of the fluid supply, means are provided for sensing fluid level at some point in the system indicative of the approach of this condition, such sensing being accomplished by photoelectric means arranged to afford reliable indication of fluid level irrespective of the transparency or opacity of the particular fluid involved. Means also are provided for shutting off flow in the event of photosensor light source failure.

Photoelectric drop sensing and timing control for intravenous feed and other flow control applications
Application Number
Publication Number
Application Date
May 13, 1969
Publication Date
September 28, 1971
Hildebrandt Herbert John
General Electric Company
G01n 21/26
G05D 07/06
A61M 05/168
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