DIAGNOSTIC EVALUATION OF A TRANSIT-TIME ULTRASONIC FLOWMETER IN NEAR CUT-OFF, TRANSITIONAL, AND STEADY FLOW REGIMES

Abstract

Modern transit-time ultrasonic flowmeters rely on internal diagnostic parameters to determine accurate measurement of the flow rate under variable hydraulic conditions. This study experimentally evaluates the performance of one such device (Flexim FLUXUS F601), using three independently acquired datasets labeled A, B, and C. Dataset A represents near cut-off conditions during system startup (around 0 m/s flow velocity), dataset C corresponds to a transitional low to high flow regime (from 0.18 to 0.7 m/s), and dataset B represents a steady flow regime (approximately 0.42 m/s). The analysis considers flow velocity, sound speed, signal-to-correlation noise ratio (SCNR), signal-to-noise ratio (SNR), automatic gain control (AGC), quality indicators, and diagnostic flags in the context of transit-time measurement theory. The results show that measurement validity depends more on hydraulic stability and signal quality than on flow velocity alone. Reliable measurements remain possible at low velocities when sound speed is consistent, and SCNR remains high. At the same time the built-in diagnostic logic rejects data as the system approaches its physical resolution limit.