Patent ID: 7644889

Claim:
A fluid sensing system, comprising: a receptacle positioned to contain a fluid; at least one radiation source positioned to emit electromagnetic radiation through the receptacle; and at least one radiation sensor positioned to receive a portion of the emitted electromagnetic radiation that passes through the receptacle, wherein the at least one radiation source and the at least one radiation sensor define, at least in part, a radiation path, and wherein the receptacle is positioned so that electromagnetic radiation that passes along the radiation path through portions of the receptacle containing fluid is focused to impinge on the at least one radiation sensor so that more emitted electromagnetic radiation is received by the at least one radiation sensor through portions of the receptacle that contain fluid than through portions that do not contain fluid, wherein the receptacle includes sidewalls having a generally uniform thickness along the radiation path, and wherein an internal volume of the receptacle along the radiation path between the radiation source and the radiation sensor is generally hollow and uninterrupted.