Explanation of the criteria for classification and numbering of components     C79.2.08
(JUN 00)
Explanation of the dates on the component's description



1.   Purpose and objectives

     To measure discharge, particularly in small or middle rivers.

2.   Description

     Transducer units are placed on both sides of the current and ultrasonic pulses are transmitted between them on a diagonal path. The difference in travel time in both directions is a measure of the flow velocity, independent of the speed of sound in the water. The measured velocity is combined with the water depth and width to give the discharge.

     The system is fully automatic and provides accurate measurements with a high reliability. The continuous measurements contribute to safety from natural disasters or accidents and the output can be used for multiple purposes. Conditions of abnormal sound propagation are detected.

     Velocities up to 4 m/s in either direction can be measured.

3.   Input

     Current speed (flow rate) and water level signals.

4.   Output

     The flow rate and water level are available as BCD signals or analogue signals (0 to 5 V, 4 to 20 mA), for telemetry or recording on site.

5.   Operational requirements and restrictions

     Except for civil engineering works necessary for construction of the facilities to install this system, the number of professional staff needed for its installation, operation and maintenance is four (4) at least.

     Ambient temperature is 0 to +40 C for the transducer and -10 to +40 C for the coder with humidity below 90 %, non condensing.

     The width of the channel must be less than 30 m. Wider channels can be measured with multiple parallel instruments. A site survey, prior to installation, is needed to decide the design.

6.   Form of presentation

     A catalogue and specifications of the system and home page are available at

7.   Operational experience

     The system has been in use since 1981 and is now installed at more than 60 sites in Japan.

8.   Originator and technical support

     Takuwa Corporation.

9.   Availability

     From the HOMS National Reference Centre for Japan.

10.  Conditions on use

     The hardware is for sale.


(First entered: 1 JAN 93

Last updated: 21 APR 00)