The measurement of wind speed and air volume in ventilation duct is obtained by conversion of measured pressure. The following is introduced by the operators of the ventilation duct manufacturer:
It is understood that in order to measure the real pressure value of the gas in the pipeline, in addition to the correct use of pressure measuring instruments, reasonable selection of measurement section and reduction of airflow disturbance have great influence on the measurement results.
The measurement section should be selected on the straight pipe section with stable air flow as far as possible. If zero value or negative value is found at any measuring point during the measurement of dynamic pressure, it indicates that the air flow is unstable, and this section should not be used as the measurement section.
When the measuring section is set in front of the elbow, tee and other special-shaped parts (relative to the flow direction of air flow), the distance from these parts should be greater than twice the pipe diameter.
When the measuring section is set behind the elbow, tee and other special-shaped parts, the distance from these parts should be greater than 4-5 times of the pipe diameter.
When the test site is difficult to meet the requirements, in order to reduce the error, the measuring points can be appropriately increased. However, the smaller distance between the measuring section and the abnormal part is at least 1.5 times of the pipe diameter.