Liquid velocity measurement system

A measurement system for measuring flow of a liquid through a channel comprising:

• transducer means oriented and positioned in a lower region of the inside of a channel to transmit and receive acoustic energy between said transducer means and an upper surface of the fluid and along a path which is essentially normal to the direction of flow through the channel;
• said transducer means comprises transmit and receive, side by side, transducers;
• signal generating means for applying an ultrasonic signal to said transmit transducer, wherein an acoustic signal is emitted along said path to the surface of the fluid and reflected back to said receive transducer;
• signal amplification means responsive to the output of said receive transducer for providing an amplified version of the output of said receive transducer over a selected frequency range;
• signal detection means responsive to the output of said amplification means for providing as an output modulation appearing on said signal;
• filter means responsive to the output of said detection means for providing as an output signals within a selected frequency range;
• amplitude limiting means responsive to the output of said filter means for providing output pulses corresponding to signal variations of a selected magnitude;
• pulse counting means responsive to the output of said amplitude limiting means for providing an output proportional to the frequency of output pulses;
• and
• velocity computation means responsive to the output of said pulse counting means for providing as an output an indication of velocity flow through said channel.