Turbine meters consist of a straight flow tube within which a turbine or fan is free to rotate, about its axis which is fixed along the center line of the tube. Straightening vanes upstream of the turbine minimizes possible rotational components of fluid flow. In most units a magnetic pick-up system senses the rotation of the rotor through the tube wall.
The turbine meter is a flow rate device, since the rotor speed is directly proportional to flow rate. The output is usually in the form of electrical pulses from the magnetic pick-up with a frequency proportional to flow rate. Turbine meter are primarily applied to measurement of clean and non-corrosive hydrocarbons.