抄録
Measurements of low range air flow velocity have been important to monitor the ventilation rate in buildings and coal pits. In recent years air flow velocity measurement, especially in the range below 0.5m/s, has become more important in testing and controlling of industrial clean rooms.
However, there has been no practical standards for low range air flow velocity so that there is a major problem of incompatibility between velocimeters made by different manufacturers.
In the present study, the standard of low range air flow velocity has been established using a towing carriage which moves on a 45 meters long rail placed in an underground tunnel. An ultrasonic velocimeter was calibrated using this apparatus in the velocity range from 0.05 to 0.6m/s. As a result of detailed estimation it is found that the uncertainty of the calibration is sufficiently minimal.
In order to supply the standard, the secondary standard velocimeters of the major manufacturers and users were calibrated. The standard established in this research is expected to make a considerable contribution to accurate measurements of low range air flow velocities in various fields.
