Detecting bubble in liq. for medical infusion - using liq. in tube as capacitor dielectric with change in value fed to comparator

摘要

The bubble of air or gas in liquid used for medical infusion is detected by coils providing coupling to capacitor formed by liq. in tubing. A bubble changes dielectric value and thus value of the capacitor. A highly stable quartz oscillator (3) has a transformer (4) coupling to the capacitor plates (1) separated by dielectric formed by liquid flowing in tube (2). Plate separation and capacitor adjustment is provided by a micrometer screw (7). Change in capacitor value due to bubble is detected for amplification (5) for a comparator (6) circuit.