I need to measure diesel output through a 12 cm dia pipe, flowing from an oil drum (8000 litre capacity) in liters. Oil flow is gravity assisted and no pump is involved. Accuracy required is 0.1 percent (+- 10 litres for full drum) or better. What kind of flow meter is best for this application, considering accuracy, safety and the application? I found ultrasonic, mechanical, capacitive, magnetic and vortex type flow meters in the catalogues. This is for an oil processing unit.

Kindly guide.