Wee,
DSA boards such as the PCI-4451 have a number of very desirable properties including high precision and a high sampling rate. The trade-off for the combination of these two properties is that the DSA boards cannot adjust their sampling rate on-the-fly. Instead they have to be stopped and reconfigured. During this reconfiguration time, the value of the board's output becomes flat and level.
If you are looking to adjust the board's output without seeing these flat spots, you have to take a different approach to programming a DSA board. Instead of reconfiguring the board, what you need to do is allow the board to continue to run (at the same output frequency), and then overwrite the output buffer that the board reads to output values. This will
allow you to output new data without the flat spots. Below you will find an example that displays this behavior.
If you determine that this is not an acceptable workaround due to the limitations on output rates, you may want to look at using a Multifunction DAQ board (60xx or 62xx) or an arbitrary waveform generator (54xx) device instead.
Best of luck with your application.
Regards,
Jed R.
Applications Engineer
National Instruments
