Why Do Differential Pressure (DP) Flow Meters Need Square Root Extraction? Many engineers know that DP flow meters use an orifice plate, venturi, or flow nozzle, but fewer understand why square root extraction is required. A DP transmitter measures differential pressure (ΔP), not flow directly. The relationship between flow and differential pressure is: Q ∝ √ΔP This means flow is proportional to the square root of the differential pressure, not directly proportional to it. Example: If the DP signal is 25% of full scale, the actual flow is not 25%. Flow = √0.25 = 0.5 = 50% of full flow Without square root extraction, flow readings will be inaccurate and misleading. Square root extraction can be performed: • Inside the DP transmitter • In a PLC or DCS • In a Flow Computer Important Troubleshooting Tip: Always verify where square root extraction is configured. Applying square root extraction in both the transmitter and control system will result in incorrect flow measurements. Have you ever faced a flow measurement error due to incorrect square root extraction settings? Share your experience in the comments. Post navigation Proximity Sensor Types Explained! RTD Working Principle Explained!
