The Yokogawa YF3INT-16 is an Electronic Totalizer (also called an Integrator) designed for use with Yokogawa's YF Series of Vortex Flowmeters. It is not a standalone device but a dedicated secondary electronic unit.
Its primary function is to receive the pulse output signal from a YF series vortex flowmeter (which is proportional to the flow rate) and calculate, display, and output the totalized flow. This means it continuously sums the flow over time to provide a reading of the total volume or mass of fluid that has passed through the meter.