To correctly choose measurement point section, to ensure the measuring point straight pipe in air flow smoothly. Therefore, measuring the cross section from the flow direction of the elbow, valve, variable diameter abnormity tube local component is greater than 4 times the pipe diameter. From the downstream direction of local bend, the structure of the variable diameter should be greater than 2 times the pipe diameter. 2. Pitot tube to measure the diameter of the specifications and selection principles are measured pipeline diameter ratio, and is not greater than zero. 02. In order to avoid interference, make error increases. Don't let the pitot tube measurement near the pipe wall. L standard pitot tube measurement shall be the total pressure port on the airflow direction, to point to the pole, static pressure on the air flow in the vertical direction. Measurement point insertion hole should avoid air leakage, and can prevent the airflow interference on the cross section. Held in S type pitot tube to measure the total pressure hole shall be on the airflow direction, the static pressure hole facing the airflow direction according to the pipeline measurement technology specifications, choose the measuring point of the measurement section. With pitot tube can only be measured on the pipeline section velocity of one point, but the average flow velocity should be used when calculating flow, because of the uneven distribution of cross section flow, so this section should be more measuring points, in order to calculate the average. Points according to the provisions of the flue measurement method according to a linear logarithmic method, can also according to the commonly used uniform area. Each pitot static pressure type joint has a tag number. Calibration coefficient and identification of single should be kept for a long time, for calculation. With the digital pressure gauge of the company, the intelligent pressure anemometer or intelligent pressure air flow meter. Can direct reading of wind pressure, wind speed, air volume.