clamp-on ultrasonic transducer

[doop4]

Hi everyone. Thanks for this wonderful forum and all your valuable contributions.


To my question ---> I would like to know why clamp-on ultrasonic transducers (the ones that are used for flow measurment in pipes) come with a piezo crystal on a wedge instead of directly mounting it on to the pipe.

Is it to do with acoustic matching ? 1/4 wavelength theory? I am not very certain so was wondering if anyone knew at all about it.

Thanks in advance

 

[zdas04]

You can purchase ultrasonic meters in either clamp-on or built into a spool. The clamp-on devices are installed on existing lines without having to blow the line down or cut in flanges for a spool, but they pay a price in accuracy for being field placed and having to go through pipe walls of varying material and consistency.

The built-in version has transducers placed by machine tools and predictable transit times through their pressure containment, but you have to modify piping to install them.

As always with measurement, you have to balance system disruption and cost against accuracy and repeatibability.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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