Even so, there are still some errors, so we can reduce the errors by filling or subtracting the water in the pipeline or adding the pump in the pipeline at the side flow rate. At the same time, the voltage, we have to ensure that under the rated voltage, the flow can be measured accurately.
As for the head of the pump, we can calculate it in this way, for example.
The head of a centrifugal pump is now measured. When the working fluid is clean water at 20 C and the measured flow rate is 60m ^ 3/h, the reading of the vacuum meter at the inlet of the pump is 0.02Mpa, and the reading of the pressure gauge at the outlet is 0.47Mpa. It is known that the vertical distance between the two meters is 0.45m. If the diameter of the suction pipe and the pressure pipe is the same, the pump head is calculated.