Fiber optic liquid level sensor

A system for detecting liquid reaching a predetermined level in a container, and comprising:

• a. an optic tubing extending in the container at an angle inclined to the vertical such that as the level of liquid in the container around the tubing rises or falls different sections of the optic tubing will be covered or uncovered by the liquid, said optic tubing having a gapped section having a gap which liquid in the container may fill with the geometric arrangement of the gap and the angle inclined to the vertical being such that light normally passes through said optic tubing and through said gap when the liquid level in the container is not in said gap but when the liquid level in the container rises into the gap, radiation which normally passes through the gap and remains in the tubing is deflected out of the gap and out of the tubing because of the different indices of refraction of the air and the liquid in the gap;
• b. a light source providing light at a first end of said optic tubing, whereby light passes into said optic tubing;
• and
• c. light sensitive means at the second end of said optic tubing for detecting the presence of light at the second end of the optic tubing, whereby the interruption of light detected by said light sensitive means signifies the liquid level being at the level of the gap in the optic tubing.