You need to take a big step back and look at what you are doing within your While loop. In every loop you are initializing communications with the instrument, configuring the STD sine wave, configuring burst mode, then turning on the output. Perhaps you are able to send all those commands to the instrument in 1.3s, but I doubt the instrument can keep up with all of those commands. So what you are getting is a garbled output of what the instrument had time to process in one loop itteration before the next loop tried to overwrite it!
What you aren't ever doing is disabling the output, closing communications with the instrument. In short you are hammering the instrument with commands, and it is doing its best to give you something...but its not what you want.
So you need to redesign your program. Probably think about how you want to trigger this burst waveform. Consider if a software trigger with all of its inexactness is adequate, or if you need a hardware trigger. Then start the coding. When you do take the initialize, the STD waveform configure, the Burst Configure and your trigger configuration all outside (before) of the While loop. Then in the loop simply trigger one measurement by software, or skip the while loop and have hardware handle triggering.
I can't tell you how best to do the measurement, you haven't provided details, but hopefully this gives you some things to think about.
Craig
