Differential Pressure Meters

Differential pressure meters (DP) include orifice plates, venturi tubes, flow nozzles, cone types, Pitot tubes, target meters, elbow tap meters and rotameters. The basic operating principle of differential pressure flowmeters is that the pressure drop across the meter is proportional to the square of the flow rate. The flow rate is obtained by measuring the pressure differential and extracting the square root.

Differential pressure meters have a primary and secondary element. The primary element causes a change in kinetic energy, which creates the differential pressure in the pipe. The unit must be properly matched to the pipe size, flow conditions, and the liquid's properties. In addition, the measurement accuracy of the element must be accurate over a reasonable range. The secondary element measures the differential pressure and provides the signal or read-out that is converted to the actual flow value.