Can't speak for designs in general, but the transducers are likely some peizoelectric ceramic, and for a basic transit time difference on typically a series of pulses nominally at 100 KHz to 1 MHz. Look for papers from Larry Lynnworth of Panametrics, which was a company that made quite a bit of the equipment for fluid, gas and multi-phase flow measurement systems with clamp-on transducers and published a number of manuals, papers, and such on the subject.
Transducers:
http://www.olympus-ims.com/data/File/panametrics/UT-technotes.en.pdfFlowmeter Overviews:
http://www.acam.de/fileadmin/Download/pdf/UFC/English/AN032_en.pdfhttp://www.asgmt.com/default/papers/asgmt2002/docs/10.pdfI used to work at Panametrics as a coop, under Larry. I don't mean as somebody who worked for him, but literally a floor under him and next to the waste pipes from the bathroom. I swear I head the plops as they fell down the pipes. Aside from that, it was one of my favorite work experiences during my student co-op years. This company was located in the Waltham Watch factory (huge old New-England style mill building) since its founding in the 1960s, and had little cubby holes and departments for everything; the flow test lab, the hot-as-hell hallway to the transducer lab and dead dumbwaiter, the whole separate division working on space weather sensors for GOES satellites (which when I interviewed for, the boss just about told me to not get ANY idea that the job was going to be cool or interesting, just a long slog doing CAD and watching tests). And all the old stuff tucked in dead-ended halls, disused rooms - I never wanted for 74 series chips, opamps and precision resistors --- wow, now that I remember, there was a stock room cage where I could walk down with a ticket and get parts ---- and the assembly area was on a whole arm of the complex with windows on the two walls and what seemed to be a quarter mile of work area, all wood floored. Charleswater ESD training. My first METCAL. Being 'talked to' for shit soldering work. The admin for my floor was a straight-up troll that lived in a dark cave of an office, and must have taken delight in sending me on demeaning tasks. First learned about FORTH there, which was used in the flowmeter computers. Making my own thermocouples, and knowing the color/types without looking at the chart. How not to build your first prototype in such a cramped way to make it impossible to rework because you obviously are going to mess up. Having a excellent sense of humor but still being serious when it comes to the work was the way to be. People can be total assholes but be competent at their job, and how to find a way to work with them. Engineers can be rock musicians on the side. Speak clearly, write clearly, and nothing really exists unless it is written, signed, and dated. That it is totally worth it to just get up and take a walk and find out what other people are working on and make friends with them - especially the machinists. And how to leave when it is time to go on a new adventure.
They're gone, but all the lessons live on, and I hope the links above help you. Thanks for the accidental trip down memory lane.
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