| 摘要 |
<p>A portable measuring device (1) is provided for automatically measuring in situ and over a gas air passage opening through which a gas flow passes, the gas flow rate. This measuring device is provided with a pressure difference gauge (29) allowing the measurement of a pressure difference between the inside and the outside of the funnel mouth (21) connected to said device after placing it for measuring purposes over said opening. The value of the measured pressure difference is thereafter converted into an electronic signal which controls the intensity of power supply to and, also if desired, its running direction, of a control fan (3) which is located in the throat cross section of the measuring device. Each measured pressure difference is reduced down to zero at an automatically selected fan speed and fan running direction (if desired too) which corresponds to the relevant gas flow rate and its relevant direction of gas flow. The air flow gas rate values become instantly readable from a reading window (11) which is connected to the measuring device.</p> |
