Appendix A Multiple-Path Transit-Time Principles Of Operation; Description; Transit-Time Operating Principles - Accusonic 8510+ series Reference Manual

A P P E N D I X A
Multiple-Path Transit-Time Principles of Operation

Description

Accusonic flowmeters utilize the multiple chordal path transit-time flow measurement technique which is
designed for accurate flow measurement (±0.5% of actual flowrate) in large pipes and open channels. The
systems can be configured to measure flow in full pipes and conduits, pipes and conduits ranging from
partially full to surcharged, and open channels. Depending upon accuracy requirements, the flowmeters can
be set up to operate 1-10 acoustic paths with cross path (cross flow) correction available on flowmeters
with 2 or more paths. A single console can be used to handle flow measurements in multiple pipes.

Transit-Time Operating Principles

The Accusonic flowmeter is connected via signal cables to multiple pairs of transducers mounted in a pipe
or channel at specific elevations. Velocity at each elevation is determined using the transit time method in
which an acoustic pulse travels downstream faster than a pulse travels upstream. A pulse of sound
traveling diagonally across the flow in a downstream direction will be accelerated with the velocity of the
water and, conversely, a pulse traveling diagonally upstream will be decelerated by the water velocity as in
the following (Fig. 1 and Fig. 2).
A-1