Abstract
1. We investigated the cause of imprecision of Mie-Univ.-type integrating flow meter when it was used in shallow stream and found the reason that it is resulted from the moment of friction at rope pully of the flow meter.
2. Friction moment was measured as 200-870g·cm in case of the float No. 37, and 910-2500g·cm in No. 42.
3. In order to revolve the pully, the buoyancy-moment, which in turn due to the depth of the water level, is necessary to overcome the friction moment.
4. Necessary increment of water level is given by eq. (1), table 2.
5. Error of flow meter due to friction moment is given by eq. (2) and fig. 1. Error of float No. 37 is less than 5% at water depth 40cm and over 8% at 30cm. Float No. 37 may practically be used for flow meter but No. 45 is not useful. Since the error of float No. 45 is sometimes 13% at 30cm deep stream.
