Doppler
LOGIQ 500 Basic Users Manual
2276612–100 Rev. 0
5–66
PW Doppler Mode Sub-Menu Page 1 (cont’d)
Wall Filter
Sample Volume (SV) Length
Description
Removes the low level, low frequency
Doppler signal caused by movement of the
vessel walls. (Also found in the CWD soft
menu.)
Changes the size of the sample volume
gate length.
NOTE: Adjustments to the sample volume
gate size are made from the center point
of the sample volume position. A larger
gate will increase the spectral broadening
affect to the spectrum.
Benefits
Eliminates unnecessary information.
Filters out low level noise above and below
the baseline so it cannot be seen or heard
on the spectrum.
A smaller gate produces accurate
sampling results because it is more
sensitive. The gate can be enlarged if
there are problems hearing the Doppler
audio or for sampling large chambers.
Values
The value can be displayed as velocity or
frequency (Setup/Custom Display
page 14). Wall Filter cutoff values are
selected as cm/s in Setup/Custom Display
page 4.
1.0, 2.0, 3.0, 5.0, 7.0, 10, 15 or 20 cm/sec.
The values could go as high as 50 cm/s
depending on the probe and the velocity
scale.
Pre-processing function.
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14 and
16 mm.
Pre-processing function.
Affects on
Other Controls
Wall filter changes with velocity scale.
Bioeffects
Acoustic
O
Adjusting this control may cause minor
changes in acoustic output. Observe the
output display for possible effects.
Output
Hazard
Summary of Contents for 500
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