Blue-White Sonic-Pro Hybrid Ultrasonic Flowmeters - Manual (Page 51)

The field on the top right displays either a speed of sound measurement value (if in
Transit Time mode) or a zero (if in Doppler mode).
When operated in the transit time mode, the flowmeter periodically calculates the speed
that sound is traveling through the fluid and displays the resulting value in meters per
second. This value is useful for determining the reliability of the measurement and also
for configuring the meter for unknown Custom Fluids.
in the index at
the end of this manual.
Should the displayed value not match, one or more of the following conditions may exist:
! The transducers are not positioned correctly
! The pipe material
!
! The fluid type does not exactly match the Fluid Type specified in the Transducer
Setup configuration menu.
! The fluid’s temperature is different than the temperature of the index values
See section 7.2.4 below for information on
The following outlines how to use the flowmeter to determine the speed of sound in a
fluid. For the flowmeter to function, the precise speed of sound does not need to be known
in advance. However, to place the transducers in the optimal location, knowing the speed
of sound in the fluid is important. The following outlines a procedure that you can follow
in determining the fluid speed of sound.
! This test can be performed with or without flow. It is recommended that the test be
performed with zero flow.
! The pipe outer diameter and wall thickness should be known precisely. It is
recommended to use a small section of pipe so that the exact dimensions can be
measured.
! The speed of sound calculation is also affected by transducer placement. Any error in
the spacing of the transducers will translate to an error in the calculated speed of
sound.
A list of the Fluid Types that
are available for selection in the meter and their sound speed is shown
The displayed value should closely match the fluid’s sound speed.
type does not exactly match the Pipe Material Type specified in
the Transducer Setup configuration menu
The pipe wall thickness does not exactly match the value specified in the
Transducer Setup configuration menu
configuring the meter for unknown or Custom
Fluids.
1) Enter all the appropriate information for pipe material and dimensions.
2) Select “custom” as the fluid type and enter a custom speed of sound for the fluid in
meters/second. Use a best first guess – if it's a water based fluid, start with
something close to the speed of sound for water. If it's an oil based fluid, use
something close to the speed of sound for oil. See the index for sample fluid sound
speeds.
3) Save and activate your configuration. Place the transducers at the spacing specified
by the meter. Press DONE. The meter will now calculate and display a speed of
sound in the upper right hand corner. If the displayed speed of sound matches that
which was entered, then that value should be used. If the displayed speed of sound is
different, or a fault occurs, change the fluid speed of sound to the displayed value or
try a new estimate and repeat step 3.
When estimating the sound speed, use a systematic approach by increasing or decreasing
your estimate by a fixed value, such as 100 meters per second.
During the run mode, the displayed speed of sound should closely match the entered
speed of sound (provided proper transducer placement and no change in temperature or
properties of the fluid such as density).
7.2.3
Sound Speed
Display
7.2.4
Measuring the
Fluid Sound
Speed
Page 51 Sonic-Pro
Industries, Ltd. Industries, Ltd.
ProSeries
by Blue-White Ind.
TM