Testing flow in hydraulic system

Northern tools sells a differential pressure flow meter for about $300.

There are many ways to measure flow and the increased cost adds accuracy and complexity. Turbines are accurate if calibrated properly and the fluid is filtered to prevent contamination of the blades in the meter. Vortex shedders are also accurate but really add to the cost and complexity. Vortex shedders count the eddies as they pass from side to side of a vane in the flow stream. That is much like counting the frequency of the boom you hear when you drive your car down the highway with the windows open. The eddies alternate from side to side and increase in frequency with increasing speed.

Coriolis mass flow meters are probably the most accurate, least troublesome and also the most expensive. They measure the coriolis effect of the fluid passing through a 'U' tube and are temperature and pressure compensated. These are typically over $5,000 for a base model.

Ever wonder why cars, trucks and tractors cost so much?

• Northern tools meter