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4-5
CQO:1010PVXFM-3
Section 4
4.4.3 NOTES ON LIQUID CONDITIONS
Successful transit-time flow measurement depends on sonic transmit signals traveling through liquid
and arriving at the receive transducer without excessive attenuation. Receive signals can be scattered
by liquids carrying dispersed particulate matter, either of a solid, non-homogeneous or gaseous
nature. This is especially true if the dispersed material is of different sonic impedance than the base
liquid. Liquids that contain an excess of gas bubbles or mineral solids may prove to be unsatisfactory
transit-time applications. However, these liquids are perfectly suitable for Reflexor flowmetering.
Liquids containing dissolved gasses or dissolved organic solids will not cause any problems for transit-
time operation.
Most liquids are excellent sonic conductors, regardless of their electrical or optical properties. Although
highly viscous liquids exhibit a greater degree of sonic attenuation, the FUH1010 operates perfectly with
the vast majority of these liquids. The
Valc % (signal strength) item on the Diagnostic Menu is a good
indicator of this condition. A low value (under 30) indicates a possible low liquid sonic conductivity, or
improper transducer installation.
4.4.4 ERRONEOUS LIQUID PARAMETER SPECIFICATION
The viscosity of the liquid is an important factor. It governs the degree of Reynolds Number compensation
that the flow computer applies to the final rate output. Therefore, flow data errors could result if you enter
an inaccurate viscosity value. Controlotron’s Technical Service Department can provide reliable viscosity
data for most liquids.
4.4.5 LIQUID COMPATIBILITY
Since our clamp-on transducer systems never contact liquid, the issue of liquid compatibility only applies
to entrained gases or mineral solid content that might impair sonic signals Since the FUH1010 is de-
signed to measure flow using both transit-time and Reflexor techniques, we can safely say that it will
operate most successfully on virtually all liquids.
4.4.6 AERATION
Undissolved gases, having very low sonic impedance, may cause sonic beam scattering. In large quan-
tities, they can reduce the sonic signal strength. Small bubbles, caused by cavitation, usually provoke
more signal loss than an equal quantity of large gas bubbles. Usually, the problem can be alleviated by
eliminating the cause. Aeration may be caused by a mixing tank, throttling valve cavitation, or air
suction upstream of the transducer location.
The FUH1010 can operate successfully with a larger amount of aeration than any other
transit-time flowmeter.
It measures and reports the aeration level as the analog output, Vaer %. This
represents the relative degree of aeration detected within the flow stream. Its computer reports the Vaer
level until it impedes operation and forces a Fault Alarm. The Vaer output accommodates applications
requiring an aeration indicator. The Vaer also appears on the display screen. The aeration percentage
can be used as an alarm relay set-point. You can set the aeration alarm setpoint such that it trips before
aeration reaches a level that impairs flow measurement.
NOTE: Before performing the installation routine, allow enough time for the liquid to flush out
all air trapped in the pipe.