An alternative gravimetric measurement standard for calibration of liquid flow meters

This paper discusses the conception, construction and validation of a gravimetric system conceived as an alternative measurement standard for calibrating liquid flow meters. The ability to evaluate a large mass of a working fluid by measuring, with much lower uncertainty, a smaller quantity of it, reflects the innovative character of the proposed calibration system. In this work, the mass of water (over 10 tons) retained in a large squared (1.50 m × 1.50 m) cross section reservoir (5 m high) is evaluated by weighing a mass of water confined in a much smaller reservoir (0.0835 m diameter, 5 m high), hydraulically connected to the first. A low capacity weigh scale (full scale: 32 kg; resolution: 0.10 g) is used to weigh, under static condition, the water in the smaller reservoir, whose liquid level is the same of the large storage reservoir. The metrological reliability of the proposed gravimetric system—assessed through the propagation of all impacting measurement uncertainties—falls in the range 0.018 % to 0.055 %, depending on the volume of the working fluid transferred throughout the calibration process (varying from a minimum of 0.001 m3 to a maximum of 0.022 m3).