Static and dynamic characteristics of a hydraulic Wheatstone bridge mass flowmeter

The hydraulic Wheatstone measuring bridge is a potential linear-flowmeter solution for direct mass flow measurements. In a concrete example of the flowmeter, four matched orifices are used as the local flow restrictors in the bridge network. This paper presents an analysis of the nonlinearity of the static measuring characteristics of the hydraulic measuring bridge, which results from the impact of the flow rate on the local pressure loss coefficient of the orifices. The results of the experimental analysis were confirmed with solutions of the physical–mathematical model of the flowmeter. Another objective of this study was to evaluate the suitability of this flowmeter for pulsating flow measurements. For this reason, a dynamic model of the flowmeter was built by upgrading the steady-state flow model with the effects of fluid compressibility and inertia. Since the flowmeter’s characteristic is linear, it was found to be unaffected by the square root errors, which is the case with standard pressure differential flowmeters. On the other hand, the flowmeter’s frequency characteristic exhibited a typical resonance, the value of which depends on the fluid and the dimensional properties of the bridge.