Weirs, variable-reluctance tachogenerators, and turbine flow meters are open-channel and direct-electrical-output flow-sensing mechanisms: a weir infers open-channel liquid flow from the head (upstream water height above the crest), derived via Bernoulli's principle and integrated over the flow cross-section to relate head to volumetric flow rate; a variable-reluctance tachogenerator produces an induced voltage from a rotating ferromagnetic-toothed wheel whose reluctance (and hence magnetic flux) varies periodically with angular position, generating a sinusoidal EMF whose frequency is proportional to rotational speed; and a turbine flow meter applies this tachogenerator principle to a blade wheel rotated by fluid flow, so the pickup's output frequency (after amplitude-normalizing signal processing) is proportional to volumetric flow rate. These concepts extend flow-measurement theory in industrial instrumentation to non-differential-pressure and electromagnetic-induction-based sensing principles.
Weirs, variable-reluctance tachogenerators, and turbine flow meters are open-channel and direct-electrical-output flow-sensing mechanisms: a weir infers open-channel liquid flow from the head (upstre…