Thanks for replying so quickly to my question. It turns out that it was a problem with my DAQcard. My signal was a 1.3Hz sinewave from a pulse generator, and the effect stayed when I changed the frequency. The graph updated smoothly, it would just do it jerkily -- the entire screen would refresh, it would pause, then refresh again. It was very dramatic and happened for a variety of frequencies, not just 1001Hz.
I used this as an axample of a larger problem I'm having, in which I use the signal from a continuous analog input acquisition to update the location of a spot in a picture control at 60Hz. I put AI read in a loop and read a certain number of scans at a time to ensure that I get a 60Hz update rate. (i.e. if my scan rate is 6000Hz and update rate
of the picture control is 60hz, I read 100 scans at a time to ensure hardware timing of the loop.) The weird thing is that the appearance of the picture control is dependent on scan rate, regardless of update rate/number of scans to read at a time. If my scan rate is 1000Hz, the spot moves smoothly (at admittedly high speed). If I set it to 4000Hz, the spot jerks around the screen and it appears to update only every tenth of a second or so. I am confused as to how the scan rate of my daq card could affect the software in this way.
By the way, I appreciate all of the help you labview gurus give all of the rest of us who try to use it for really weird stuff. 🙂
--Melinda
