# Volumetric Flowmeters with Frequency Output

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I am reading about Flow Calculations, and compensation formulas that were put in the flow computer to compensate for the pressure and temperature.

I am reading about Standard/Corrected Volumetric flow from 2 sources.

The first from 415 models flow computers (manual from our server) and the other from this website
http://iom.invensys.com/EN/pdfLibrary/WhitePaper_Foxboro_VortexSheddingTutorial_01-10.pdf

Which talks about Vortex Shedding flowmeters.

volumetric Flow (415 flow computer)

Qvb = (f/k)(Pf/Pb)(Tb/Tf)(Zb/Zf)

Qm = (density_b)(Qvb)

Qvb = Volume Corrected Flowrate
Qm = Mass Flowrate

another website (vortex shedding website)

Qv = Standard Volumetric Flow
Qm = mass flowrate

Qv = (density_f/density_b)(f/k)
Qm = density_f*(f/k)

Why is it in one source it is multiplied by density of flow/density at basic conditions?

While the other source:
multiplied by (Pressure of flow/pressure of base)*(Temperature of base/Temperature of flow)*(compressibility of base*Compressibility of flow)

Thank you in advance.

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