can the "chart-speed" be set 
Author Message
 can the "chart-speed" be set

Howdy,

I need to chart 2000 values per second. The chart however charts with
the highest speed possible. How do I set the scroll-speed of the chart,
so the user gets the impression of a smooth charting motion? Do I need
to control the speed with which the data is passed to the chart?

Thanks,

M Soderberg

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Mon, 28 Jan 2002 03:00:00 GMT  
 can the "chart-speed" be set

Quote:
> I need to chart 2000 values per second. The chart however charts with
> the highest speed possible. How do I set the scroll-speed of the chart,
> so the user gets the impression of a smooth charting motion? Do I need
> to control the speed with which the data is passed to the chart?

With today's computers, you can expect anywhere from 15 to about
150 updates per second depending on the size of the chart, the
update mode, and to a large extent on the depth of the screen.

As you guessed, you control the speed by how the data is written
to it.

To tune it, copy your chart into another VI.  With 2K points per
second, you probably want to set the chart X scale to show at least
6000 points or so.  That will give you three seconds to see a point
before it leaves the screen.  You may need to update the chart
history size to get enough points on the chart scales.  Then
generate simulated data and determine how many updates you can
achieve per second.  Adjust the time scale and the number of
points per update to get your 2K/sec display speed.  It is best
to have the points per update adjust by plotting whatever is in
the DAQ buffer.

If the chart isn't that smooth at that point, you should try
to speed it up by changing the size or display depth.  It is
amazing, and a little disturbing how much slower video drivers
are in TRUE color.  Most of the machines I've seen are about
three or four times faster in thousands of colors than in
millions.  256 colors is usually about two or three times faster
still.  Other graphic affects like grids, points, line width and
dashes also have some affect, but not that much.

Greg McKaskle



Tue, 29 Jan 2002 03:00:00 GMT  
 
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