The working principle of the standard volumetric tube method is based on the volumetric method (standard volumetric method), but it is a dynamic measurement. The standard flowmeter comparison method is to connect the flowmeter to be calibrated and the standard flowmeter in series on the pipeline flowing through the test fluid. The error is calculated by comparing the two measured values. The accuracy of the standard flowmeter is 2 to 3 times higher than that of the schooled flowmeter.