Proving is a method of checking a measuring device against an accepted standard to determine the accuracy and repeatability of that measuring device. PRECISION TURBINE FLOWMETERS should be proven immediately after repair, removal from service for any reason, when changing products, product viscosity changes, or charting the flow patterns of the flowmeter over a time period. In general, provings should be recalibration if the rotor is damaged or has been changed.

There are several different methods of proving. Volumetric proving consists of a measured volume of fluid being compared to a known standard, such as a seraphin can or piston prover. Gravimetric proving entails measuring weight of a fluid by scale or load cell and converting it by a known formula. Master-meter proving is the comparison of a test flowmeter to another flowmeter previously calibrated in one of the above methods.  Bell proving is for gas measurement.   Volumetric and gravimetric proving are primary methods while master-meter proving is a secondary method. EFR design meters are normally factory calibrated using a gravimetric (primary) method at 10 or more points with documentation supplied to the user.