Sensing systems, connectors, and methods include a housing, including a sensor and a locking mechanism, a junction, and a membrane. The junction includes a fluid inlet, a fluid outlet, and a receiving mechanism. The receiving mechanism is removably attachable to the locking mechanism. The membrane is disposed within the junction, and is in fluid communication with the fluid inlet and the fluid outlet. The sensor senses a property of a fluid across the membrane when the locking mechanism is attached to the receiving mechanism.