BNC 1420 - Video Microscope - Manual (Page 38)

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NOTE: If the probe is located in an area of very slow flow then
subtracting the background could delete active particles.
c. Deconvolve Autocorrelation is an advanced option for
high precision measurements. This option deconvolves the
cross correlation by the autocorrelation, which can remove
the effects of blur and particle size such that each particle is
treated as a single point. It is most useful when the signal-
to-noise ratio is extremely high.
5. The Show Field options control which data are displayed for each
probe window:
a. Cross correlation determines how far the particles move
between frames (or between every few frames, based on the
Frames Skipped option). This field is a good diagnostic
tool to help you optimize experiment parameters. The red
dot will move further from the center as the flow velocity
increases. The dot should be small and well defined to
achieve the most reliable measurements. If the flow is too
fast the red dot will move outside of the window, and
scopePRO will not be able to measure the velocity. In this
case, increase the window size, which will improve the
signal-to-noise ratio.
b. Autocorrelation is an indicator of resolution. The mass at
the center of the window will become sharper with smaller
particles and better focus.
c. Mean shows the data that is being subtracted as part of the
Background (based upon the Background % described
above). Showing the Mean can be helpful for highlighting
stuck particles and other anomalies in the flow.
d. RMS is an indicator of the amount of useful signal
available for the calculations.
e. Show Text turns on and off the text-based velocity display.
f. Show Vector displays an arrow in the direction of the flow.
The size of the arrow will change with velocity. You can
also set the Scale to increase or decrease the arrow size.