The purpose of manual calibration of impeller is to correct the balance of impeller and reduce vibration. Therefore, manual calibration should be judged from vibration to determine the position and weight of the counterweight or reduce the weight, which has a great relationship with the experience of the verifier. If the impeller width is relatively small, one-sided balance correction can be used, and if the impeller width is relatively large, double-sided balance correction should be used.

1) Determine the position of the counterweight: firstly, start the fan, put your hand on a certain surface of the fan and feel its vibration; After stopping, add a counterweight to the balance surface of the impeller (estimate the approximate weight according to the vibration), restart the fan, and feel the vibration by hand. If the vibration intensifies, it means the position is wrong. Add a counterweight near the symmetrical position of the previous position, then start the fan to feel the vibration, constantly change the position of the nearby counterweight, and repeat it for many times until the vibration is the smallest, and determine the position of the counterweight.

2) Determine the weight of the counterweight: at the determined position, slightly increase or decrease the weight of the tested counterweight, start the fan to feel the vibration amplitude, and repeatedly increase or decrease the weight until the vibration meets the requirements.

Finally, firmly fix the counterweight with the same weight or subtract the same weight from its symmetrical position. Just start the fan and make sure it is correct.