Multifunction DAQ

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continuous sine sweep

I need to create a analog output sine sweep of around 20kHz with very
small increments (around 20Hz, i.e a resolution of 1E-3); this cannot be
done by changing the update rate (constant at 4Msamples/s which gives
around 200pts per period). Instead I calculate a sine of say 10 periods
using first 2000, then 2002, 2004 points etc. which gives me the desired
resolution. Each frequency needs to be sent to the output for about 1s,
so I use continuous buffered output generation.
The problem arises when I change from one frequency to another - my
application demands this to be done on the fly, i.e. without any major
phase change in between, let alone any dead time without any signal at
all. As my buffers have different lengths (i.e. 2000,
2002 etc.), I have
not managed to do this, i.e. I have a dead time of several ms. Is there
a way around that problem? - Any help would be very much appreciated...

Hardware: PCI 6110E with LABVIEW 5.1

Markus Wiesendanger
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