Compare orifice meter and venturi meter for flow measurement.

Both measure flow using differential pressure from Bernoulli's principle. Orifice meter: simple flat plate with hole, low cost ($100-500), easy installation, but high permanent pressure loss (40-80% of differential), Cd ≈ 0.6-0.65. Venturi meter: converging-diverging design, higher cost ($1000-5000), requires more space, but low permanent loss (10-20%), Cd ≈ 0.95-0.99. Venturi better for large pipes, abrasive fluids, and when pumping cost is significant. Orifice preferred for small pipes, clean fluids, and limited budget. Both require straight pipe runs upstream (15-40D) for accuracy.