A flow meter includes an image sensor, a coupler, a support member and one or more processors. The coupler is adapted to couple to a drip chamber. The support member is operatively coupled to the coupler. The image sensor has a field of view and is operatively coupled to the support member. The image sensor is positioned to view the drip chamber within the field of view. The processor receives data from the image sensor and is configured to: receive a first image from the image sensor, compare the first image to a second image, and generate a difference image based upon the comparison between the first and second images.