Dynasonics TFXM Series Ultrasonic Multi-Channel Flow Meter - Manual (Page 72)

Rev. 8/02 -4. 5- TFXM
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The Damping value is increased to increase stability of the
flow rate readings. Damping values are decreased to allow
the flow meter to react faster to changing flow rates.
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Low Flow Cutoff is entered as a percentage between MAX
Flow and MIN Flow and influences how the flow meter will act
at flows very near zero. Generally, an entry of 1% provides for
a stable zero indication, while providing a 100:1 turndown ratio
for measurements.
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Low Signal Cutoff is a relative value that should be entered
after a successful flow meter startup. For an initial value,
enter 5% [Signal Strength indications below 3% are
considered to be below the noise ceiling and should not be
indicative of a successful flow meter startup.] The entry has
three purposes: It provides an error indication—Low Signal
Strength [Error 0010 on the TFXM display] when liquid
conditions within the pipe have changed to the point where
flow measurements may not be possible. It warns if the pipe’s
liquid level has fallen below the level of the transducers. It can
also signal that something with the flow meter installation or
configuration may have changed. Examples would include
such things as the couplant used to mount the transducer has
become compromised, a cable has become disconnected or a
pipe size setting has been altered.
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Substitute Flow is used to provide an indication and output
that signifies that an error exists with the flow meter or its
setup. It is set as a percentage between MIN Flow and MAX
Flow. In a uni-directional system this value is typically set to
zero, to indicate zero flow while in an error condition. In a bi-
directional system, the percentage can be set such that zero is
displayed in a error condition. To calculate out where to set
the Substitute Flow value in a bi-directional system perform
the following operation:
Substitute Flow = 100 x MAX Flo w ____
MAX Flow + MIN Flow
SOFTWARE UTILITIES