Processing Magazine

The difference between paths and chords in ultrasonic flowmeters

July 31, 2012

What is the difference between a chord and a path in an ultrasonic flowmeter? I find that different vendors use these terms differently, and some like KROHNE and Faure Herman use the term "beam."

I recently raised this issue at the CEESI Ultrasonic Meter Workshop in June, where I discussed it with several suppliers. My best understanding is that a chord is an ultrasonic signal that goes from one side of a pipe to the other, while a path goes from one side of a pipe to the other and back. But sometimes a chord does not go through the center of the meter, but only along the upper or lower side.

Can anyone explain the Faure Herman meter to me? They call this an 18 path meter with 36 transducers. Are some of these paths reflected paths? Does this generate higher accuracy?

The new Q.Sonic Plus from Elster has 6 paths and 16 chords. At least Elster distringuishes between the two.

I think that companies like to count as many paths or chords or beams as possible in their ultrasonic flowmeters because it makes them sound more accurate, but I‚Äôm not sure that everyone is using the terms in the same way.