Abstract

A fluid bypass type flowmeter has a main passage which is configurable to various effective diameters by selectably adding pre-defined additional cross-sections comprised of an adjustable laminar flow element located within a bore for fine adjustm=ent of the full-scale range of the flowmeter, and an adjustable restriction secondary passage for crude adjustments of the range of the meter. With adjustment of the flowmeter, all or a selected portion of the flow to be measured can be diverted through the secondary passage, where a flow measuring device is located, thereby allowing the flowmeter to operate at or near its full scale and thereby improving the accuracy of the flowmeter over various ranges of flow rate. A laminar flow element is employed in the main passage so that the pressure drop across the element varies linearly with flow rate and, accordingly, the ratio of diverted to un-diverted flow is a constant ratio even though the flow rate varies. The secondary passage adjustable restriction is also designed to give laminar flow to obtain linearity over flow rate variations.