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 in communication with the image sensor to receive data from the image sensor, wherein the at least one processor is configured to: receive a first image from the image sensor, compare the first image to a second image wherein the second image contains a pattern having a plurality of lines, and generate a difference image based upon the comparison between the first and second images.