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1. Electromagnetic flowmeter: Changes in physical properties of the fluid being measured, such as viscosity and density, can have an indirect impact, but this indirect effect can be taken into account when correcting for those property effects. Due to the complexity of the structure and shape of flow meters, as well as the variability in their manufacturing and assembly processes, it is generally impossible to use computational methods to accurately adjust their internal cavities in response to changes in operating conditions. It is also not possible to derive empirical formulas that meet accuracy requirements for all flow meters based on experimental data. 2. Broadly speaking, flow conditions such as the uniformity of the medium being measured, its gas (liquid) content, and impurity levels also fall under the category of operating conditions for flowmeters. However, their impact on the performance of flow measurement instruments is more complex, and sometimes it is difficult to address these issues through online real-time calibration. 3. Turbine flowmeters: For volume flowmeters, during type certification, prototype testing, or quality inspection checks, when a naturally aspirated engine is modified into a turbocharged engine – whether using a exhaust gas turbocharger or a mechanical turbocharger – vortex flowmeters encounter the problem of high intake air temperature. The intake air temperature of a naturally aspirated engine remains relatively constant regardless of the engine’s operating conditions; whether it is installed in an air flowmeter, on the intake manifold near the throttle, or in the air box, the temperature difference is minimal. As for velocity-type turbine flowmeters, changes in operating conditions lead to variations in their flow area, which in turn results in changes in the instrument’s coefficient. If the operating conditions of the flow meter during calibration can be the same as or similar to those in actual use, then offline calibration will meet the requirements. However, due to the complexity and variability of operating conditions, offline calibration often fails to replicate actual operating conditions; only online, real-flow calibration can address the issue of high-accuracy flow measurement, otherwise additional errors must be taken into account.