The inherent linearity of a turbine flowmeter is a tremendous advantage over nonlinear flow
elements such as venturi tubes and orifice plates because this linearity results in a much greater
turndown ratio for accurate flow measurement. Contrasted against common orifice-type meters
which are usually limited to turndown ratios of 4:1 at best, turbine meters commonly exceed
turndown ratios of 10:1.
If pickup signal frequency directly represents volumetric flow rate, then the total number of
pulses accumulated in any given time span will represent the amount of fluid volume passed through
the turbine meter over that same time span. We may express this algebraically as the product of
average flow rate (Q), average frequency (f), k factor, and time