CST FSI-T10-001 1" FSI T Series Standard Output Tee Type Flow Sensor. Creative Sensor Technology FSI series flow sensors feature proven impeller based technology designed for flow monitoring/flow control applications in irrigation, water conservation and related industries. The term sensor is used because this measurement device produces an output signal rather than a visual display. The PVC tee type sensor with socket connections is offered for service in all class and schedule rated PVC piping systems.