Study on zero drift factors in micro-liquid flow measurement using Coriolis mass flowmeters

For the measurement of small flow rates, Coriolis mass flowmeters are usually designed with a single tube structure, with no bypass or converging flow structures upstream or downstream to improve measurement sensitivity. However, it has been found that preheating flowrate and measurement sequence affect zero-point stability. In this study, a Coriolis mass flowmeter with single tube double-ring shape was made, and temperature sensors were placed on the upstream and downstream isolation plates, the gear pump, and the surrounding environment to record the in-line and environment temperature changes throughout the measurement process. The experimental results show that due to the obvious temperature rise generated by the gear pump during operation, part of the heat will be taken away by the flowing medium, thus forming a temperature gradient in the pipe containing the measured flowmeter. For the single tube type Coriolis mass flowmeter, the internal pipe temperature gradient will cause a more obvious zero-point drift than the dual pipe parallel structure, and cannot obtain a stable zero point in a short time. Therefore, this paper suggests avoiding temperature abrupt changes by matching the preheating flow and measurement sequence, thereby achieving better measurement results for small flow rates.