Mace HVFlo XCi, Product Manual

Page: 161 / 255

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Wind effect filter
” - Under certain field conditions, a stream may move in a positive direction but the
prevailing winds may come from the opposite (negative) direction. The effect of this on Doppler
ultrasonic processing is that a strong negative Doppler shift may be “seen” as well as the actual
positive shift of the stream itself. In some cases the shift caused by the winds may overwhelm the shift
from the slower moving water flow and cause erroneous flow rate readings. The “Wind effect filter” is
built in to allow the user to overcome such sources of error.
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“ Disabled ” - When checked, all filtering is off.
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“ Positive ” - When checked, all negative velocity components are filtered out.
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“ Negative ” - When checked, all positive velocity components are filtered out.
WARNING: The user MUST check that the “Wind effect filter” does not cause
real velocity data to be ignored
Velocity peak threshold
Doppler shifts that are unrelated to the measurement of velocities in a stream are often called “signal noise”.
This “noise” can be a result of several different factors including:
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Electromagnetic interference;
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Reflections of signals from other echoes.
In some situations background noise may interfere with the calculation of correct average velocity readings.
MACE XCi instruments feature a “noise filter” called a “ Peak threshold ”.
MACE XCi User Manual - 161 -