Liquid metering system

A system capable of infusing a pharmaceutical liquid into a patient comprising

• a) a conduit along which said liquid flows, a portion of said conduit having a light transmitting wall,
• b) a heater adapted to heat a portion of said liquid at a certain position along said conduit,
• c) a source providing illumination of said liquid in said conduit through said light transmitting wall at a position downstream from said liquid heater such that no interference pattern is created by reflections of the illumination by the walls of the conduit, and
• d) an optical sensor positioned to receive only a portion of said illumination reflected from the first transmitting wall liquid interface such that said optical sensor detects a change in the intensity of said reflected illumination due to the change in the index of refraction of said heated portion of said liquid as it moves along the conduit, thereby enabling the measurement of flow of the liquid through the conduit.

The method of measuring liquid flow along a conduit with a light transmitting portion comprising the steps of

• a) healing a portion of the liquid at one location along the conduit,
• b) illuminating a downstream location of the conduit through the light transmitting portion of the conduit with illumination from a light source such that no interference pattern is created by reflections of the illumination by the walls of the conduit,
• c) detecting a change in the intensity of only said illumination reflected from the first transmitting wall liquid interface at the downstream location of the conduit when the heated portion of the liquid passes the downstream location due to the change in the index of refraction of the heated portion of the liquid, and
• d) calculating the time required for the heated portion of the liquid to travel from the location of the heat source to the location of the illumination.

A liquid metering system comprising:

• a conduit along which liquid flows, a portion of the conduit having a wall;
• a liquid heater that heats a portion of the liquid at a first position along the conduit;
• a light source directing a beam of light through the wall for illumination of the liquid in the conduit at a second position downstream of the first position such that no interference pattern is created by reflections of the illumination by the walls of the conduit;
• and
• an optical detector positioned to detect a change in an the intensity of only the portion of the beam generated by reflection at a first interface between the wall and the liquid;
• wherein the change in the intensity is caused by the change in the index of refraction of the heated portion of the liquid passing the second position.

A method of metering a liquid comprising the steps of:

• heating a portion of the liquid at a first position along a conduit wherein the conduit has a wall at a second position downstream from the first position;
• directing a beam of light through the wall such that no interference pattern is created by reflections of the illumination by the walls of the conduit;
• and
• detecting a change in the intensity of only the portion of the beam of light reflected from the first interface of the liquid and the wall at the second position;
• wherein the change in the intensity is caused by the change in the index of refraction of the heated portion of the liquid passing the second position.