An electro-optical meniscus-sensing system for a pressurized flush bottle

¹ Department of Pediatrics, University of Florida School of Medicine, Gainesville, Florida

A pressurized flush bottle system is used in some laboratories to ensure patency of indwelling catheters and needles. Some method must be utilized to monitor the fluid level in the bottle since complete emptying of the fluid would allow air under pressure to pass into the circulatory system. An electro-optical device is described which will sense a predetermined level of saline. A light source is mounted in a bottle holder assembly almost opposite and slightly below a photoresistor. At any level of fluid, some light from the exciting lamp is reflected from the meniscus causing a shadow immediately above the fluid level. When the meniscus falls below the photocell level, the decrease in light intensity increases photocell resistance which causes the transistorized circuit to activate audio and visual warning devices.

Submitted on October 26, 1964