Drop volume measurement system

Apparatus for measuring the volumetric flow rate of a fluid passing through a transparent drip chamber having fluid inlet means at its upper end and fluid outlet means at its lower end, said apparatus comprising:

• a drop orifice at the top of said drip chamber opening freely into unobstructed interior space of said drip chamber, said drip chamber having a width between laterally spaced side walls separated by an uninterrupted space such that drops sequentially formed one at a time at said drop orifice may freely fall through said drip chamber without contact with any confining wall surface;
• first sensor means positioned in proximity to said drip chamber for sensing drop presence and emitting a first signal in response thereto, said first sensor means comprising a first light emitting source noninvasively located externally of said chamber and generating a first sensing field projecting generally transversely across said drip chamber and an aligned light detector positioned outside of said chamber, said first light source and its generated sensor field being so positioned a predetermined distance below the outlet of said drop orifice that each separate drop does not enter the first sensing field until the drop is in free fall;
• second sensor means positioned in proximity to said drip chamber for sensing drop presence and emitting a second signal in response thereto, said second signal being utilized in cooperation with said first signal to determine a drop size dimension, said second sensor means comprising a second light emitting source noninvasively positioned externally of said chamber and generating a second sensing field projecting generally transversely across said drip chamber and a second light detector in alignment therewith outside of said chamber, said second light source being vertically spaced below said first light source a predetermined distance along the height of said drip chamber, whereby two vertically spaced sensor fields are established utilizing any commercially available drip chamber;
• circuit means for receiving the signals emitted by said first and second sensor means, comprising means for determining a drop size dimension based on a predetermined time correlation of and between said signals for a specific drop, and means for determining the volumetric flow rate based on the number of drops sensed by either the first or second sensor means in a unit of time and the determined drop size dimension;
• and
• said means for determining a drop size dimension comprises timer means operatively associated with said first and second sensor means to receive said first and second signals therefrom and functioning to determine the vertical dimension of a drop in the direction of drop passage through said drip chamber based on the time duration of said first and second signals as a measure of the time for a specific drop to pass through each of said two sensor fields and on the time interval for a specific drop to pass through a predetermined distance between the two sensor fields.

A process for measuring the volume of a drop of a liquid utilizing a transparent drip chamber comprising the steps of:

• generating a first sensing field generally transversely of a transparent drip chamber by a first light emitting source aligned with a first light detector;
• simultaneously generating a second sensing field generally transversely of said transparent drip chamber at a predetermined, vertically spaced location below said first sensing field by a second light emitting source aligned with a second light detector at said vertically spaced location;
• introducing discrete drops of liquid sequentially into the unobstructed, open space of said drip chamber from the top of said chamber so that the drops fall one at a time through said first and second sensing fields in an unconfined, free falling state;
• producing a first signal in response to the passage of a specific, free falling drop into and through said first sensing field;
• producing a second signal in response to the subsequent passage of said specific, free falling drop into and through said second sensing field;
• and
• measuring the time duration of said first and second signals and the time interval between the start of said first signal and the end of said second signal for said specific, free falling drop and thereby determining the vertical dimension of said specific drop in the direction of drop fall through said chamber based on a predetermined algorithm utilizing said time measurements, and thereafter calculating the volume of said drop utilizing said vertical drop dimension.