1. A flow meter, comprising: a coupler adapted to couple to a drip chamber; a support member operatively coupled to the coupler; an image sensor having a field of view and operatively coupled to the support member, wherein the image sensor is positioned to view the drip chamber within the field of view; and at least one processor operatively coupled to the image sensor to receive image data therefrom, wherein the at least one processor is configured to: capture an image including an image of the drip chamber using the image sensor having the field of view including the drip chamber; subtract the image from a dynamic background image to thereby generate a difference image; and examine the difference image to determine whether a free flow condition exists.