Instead of removing flowmeters from service for recalibration, the unit allows users to "bring the calibrator to the flowmeter." This affordable, documenting field flow calibrator is intended for in-line calibration and validation of meters using the actual process liquid. It is compatible with any meter with an electronic output or visual indicator. Rugged, lightweight and compact, the calibrator is a handheld unit that eliminates the need to carry a laptop computer into the field. Two dual-rotor turbine flowmeters, which provide exceptional repeatability of +/-0.02%, enable the system uncertainty to be <+/-0.25% of reading. The unit automatically selects the appropriate master meter, based on the current flow rate. Flow conditioners are built into the manifold, as well as the temperature sensor. The calibrator reads signals from the master meters, the flowmeter under test and a fluid temperature sensor. The embedded flow computers process these signals to enable viscosity compensation, linearization and processing of the UUT output.