The discharge line of a centrifugal pump in a wastewater treatment plant often incorporates a stainless‑steel flow control device with a VDC PNP connector. Mounted directly on the pipe, the unit senses the moving liquid and translates the measurement into a voltage signal that the plant’s PLC receives. Operators use the live signal to close the feedback loop that regulates the variable‑frequency drive of the pump, keeping the flow rate within the prescribed range. Because the housing is stainless steel, the sensor survives the aggressive chemistry of the influent without corrosion, reducing maintenance intervals. The PNP output simplifies wiring, allowing a single‑ended connection to the control cabinet and avoiding the need for external signal conditioning. In a typical scenario, a sudden drop in flow triggers an alarm on the operator’s HMI, prompting the system to increase pump speed automatically. The same device can be fitted on a chemical dosing line, where precise flow monitoring is required for batch consistency.