Flow measurement and measuring instruments in the traditional sense of measurement scales are very different, it is not simply connected to the flowmeter, the boot will be able to achieve the purpose of measurement. Flow measurement is a strongly dependent on the use of measurement techniques, flow meters to work depends on: First, the environmental conditions (ambient temperature, humidity, vibration, etc.); Second, the fluid conditions (temperature, humidity, pressure, composition, flow Status, etc.); Third, the power conditions and other conditions. About the calibration of the pump flow: The calibration of the pump flow is measured when the pump is not connected with any damping components (such as pipes, valves, etc.), so as to truly reflect the working capability of the pump itself. Each customer using the pump will be based on their needs to connect a variety of different pipes, valves, flow meters, etc., to form a complete gas system. At this point, the system's gas flow is not equal to the pump's flow, because of the pressure loss of the various gas circuit components, thus attenuating the flow. About flowmeter: Some people use pipelines directly connected to the flowmeter and pump used to measure the pump flow and found that the measured value is smaller than the calibration value, the replacement of different flowmeters have different measurements. This is because the flowmeter itself is also caused by pressure loss. Different pressure loss of different flow meter, the attenuation of the flow will be different, resulting in different test results. Therefore, to determine the flow of the pump, we should leave a margin according to the size of the resistance of the pneumatic system.