Fluid processing cassette and sensor coupling system and method

A fluid processing system comprising:

• a cassette comprising a molded body having a plurality of valve stations and at least one pressure sensing station, wherein the pressure sensing station comprises a cap having an opening extending beyond the molded body;
• a loading area configured to receive and hold the cassette, and configured to position the cassette onto a valve and sensor assembly, wherein the valve and sensor assembly comprises valve actuators and at least one pressure sensing transducer comprising a sensor post, the valve and sensor assembly configured to align respectively with the plurality of valve stations and the pressure sensing station;
• wherein the opening of the cap is formed by an inner wall having a first diameter, an outer wall having a second diameter, and a contact surface connecting the inner and outer wall,
• wherein the contact surface includes a varying diameter that decreases from the second diameter to the first diameter;
• and
• wherein the sensor post comprises a ring disposed around a cylindrical body and positioned to engage with the contact surface of the cap to form a seal.