An interesting characteristic of transit-time velocity measurement is that the ratio of transit time
difference over transit time product remains constant with changes in the speed of sound through
the fluid46. When this equation is cast into terms of path length (L), fluid velocity (v), and sound
velocity (c), the equation simplifies to Q = 2kv
L , proving that the transit-time flowmeter is linear just
like the Doppler flowmeter, with the advantage of being immune to changes in the fluid’s speed of
sound. Changes in bulk modulus resulting from changes in fluid composition, or changes in density
resulting from compositional, temperature, or pressure variations therefore have little effect on a
transit-time flowmeter’s accuracy