|
[Instrumentation Table of Contents]
[Sensors and Transducers Suppiers Menu]
Devices such as ultrasonic flow equipment use
the Doppler frequency shift of ultrasonic signals reflected
from discontinuities in the fluid stream to obtain flow
measurements. These discontinuities can be suspended solids,
bubbles, or interfaces generated by turbulent eddies in the
flow stream. The sensor is mounted on the outside of the
pipe, and an ultrasonic beam from a piezoelectric crystal is
transmitted through the pipe wall into the fluid at an angle
to the flow stream. Signals reflected off flow disturbances
are detected by a second piezoelectric crystal located in the
same sensor. Transmitted and reflected signals are compared
in an electrical circuit, and the corresponding frequency
shift is proportional to the flow velocity.
|
