Abstract

A bubble detector for a liquid stream flowing within a conduit comprising a walled chamber communicating with the conduit interior, the chamber being positioned to trap and accumulate bubbles entrained with the liquid stream. A window in the chamber wall for optically examining the chamber, the window having its inner surface positioned to provide an interface with the chamber contents. Means for distinguishing between liquid and gas in the chamber comprising a light source positioned to direct its light toward the window inner surface, and a light sensor oriented to receive light reflected from the window inner surface the light source being positioned at such angle to the window inner surface that transmission of light with refraction occurs when liquid is present in the chamber and total internal reflection occurs when gas is present in the chamber. And an output device responding to the sensor for taking an action when a predetermined volume of bubbles have accumulated in the chamber.