A flow rate measuring device having a housing for enclosing and preventing a removable ramp from being exposed to ambient light. The ramp includes an upper transparent section and a lower transparent section enabling a flowable substance to flow therebetween. A timing circuit connected to a first photo detector and a second photo detector below transparent sections of the ramp determines amount of time for a flowable substance to flow between the first photo detector and the second photo detector. Artificial light sources above the photo detectors are included within the housing.