Patent ID: 8231566

Claim:
A positive displacement flow sensor for use in connection with a medical fluid infusion system including an administration set having an administration tube, the positive displacement flow sensor comprising: a housing having an inlet port and an outlet port, the ports being operatively connected to the administration tube; a first rotor positioned within the housing between the inlet port and the outlet port; a second rotor positioned within the housing between the inlet port and the outlet port, the second rotor being positioned adjacent to the first rotor, the first and second rotors each having a plurality of lobes, the lobes of the first rotor engaging the lobes of the second rotor in a gearing relationship and arranged to rotate in response to a flow of medical fluid in the administration tube for detecting flow of the medical fluid in the administration tube; and a cover enclosing the housing such that when the medical fluid flows into the inlet port it causes the first rotor to rotate and thereafter the medical fluid exits through the outlet port, wherein the flow sensor is configured to provide at least one of an electrical or optical flow rate signal to a reader, wherein the cover has a substantially opaque pattern imposed thereon that corresponds to a shape and size of the first rotor, substantially prevents light from passing through the pattern and provides an optical contrast between said pattern and at least the first rotor.