| 摘要 |
An acoustic fluid flow meter comprising timing means (10) for determining downstream (Td) and upstream (Tu) transit times values of acoustic pulses transmitted between acoustic signal transceivers (7,8), operable alternately as generators and receivers, with and against the direction of fluid flow. Additionally there is provided an error signal indicator (16) operable to receive the determined transit time values and to output an error signal indicative of a false flow reading if their sum and/or difference, particularly the sum of determined values (Td,Tu), differs from a corresponding control value by a predetermined amount. <IMAGE>
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