Device for compensating for pressure differences across valves in cassette type iv pump

A pump (10) employed to infuse a fluid flowing from a source (12, 14) to a patient, including: (a) a disposable cassette (15) having a housing defining a fluid path from an inlet port (16) which is adapted to couple in fluid communication with the source (12, 14), to an outlet (38) which is adapted to couple in fluid communication with an infusion site in the patient, and including a pressure sensor input (24) that produces a signal indicative of a pressure near the inlet port (16), and a pressure sensor output (34) producing a signal indicative of a pressure near the outlet (38 ), said fluid path: (i) a chamber (30) covered by an elastomeric membrane; (Ii) an inlet valve; and (iii) an outlet valve; (B) a drive unit (19) adapted to engage with the disposable cassette; and (c) a control unit.