Air bubble detector

In association with a generally cylindrical transparent intravenous fluid conduit, the inner wall of said conduit being reflective to light, an air detector comprising:

• (a) a pair of detector units spaced from one another in the direction of the axis of said conduit, each said detector unit including
• (i) a light course positioned alongside said conduit
• (ii) first light-detecting means positioned alongside said conduit at a location generally diametrically opposite and facing said light source and adapted for receiving direct light passing through said conduit;
• and
• (iii) second light-detecting means positioned alongside said conduit between said light source and said first light-detecting means and adapted for receiving reflections from said inner wall of said conduit;
• and
• (b) logic means coupled to said first and second light-detecting means of each of said detector units and arranged to produce a particular signal when, and only when, in each of said detector units, the light levels detected separately and simultaneously by said first and second light-detecting means bear a predetermined logical relationship to one another.

An air detector for use in conjunction with a generally transparent fluid conduit, the inner wall of said conduit being reflective to light, comprising:

• (a) a light source;
• (b) first light-detecting means so positioned as to detect light traveling from said light source along a first path traversing said fluid;
• (c) second light-detecting means so positioned as to detect light traveling from said light source along a second path involving a reflection from the inner wall of said conduit but not traversing said fluid;
• and
• (d) signal-producing means associated with said first and second light-detecting means and arranged to produce a particular signal when and only when, the levels of light detected separately and simultaneously by said first and second light-detecting means bear a predetermined logical relationship to one another.

A method of detecting air in a transparent fluid conduit, the inner wall of the conduit being reflective to light comprising the steps of:

• (a) transmitting light along a first path traversing said fluid, and along a second path involving a reflection from the inner wall of said conduit but not traversing said fluid;
• (b) separately and simultaneously detecting the relative levels of light transmitted through said paths;
• and
• (c) producing a particular signal representative of whether said light levels are substantially the same or substantially different.