Hello Mr._Bass,
The NI-9265 will update its output values every 9.5 us, which computes to just over 100,000 samples per second. As such, the hardware itself has the capability to maintain this speed. In terms of your system and the expected amount of jitter, this number will vary quite a bit depending on your machine. If you have typical tasks such as antivirus, firewalls, or anything else that Windows runs in the background, jitter will be increased. On average, the amount of jitter in a windows system is on the order of hundreds nanoseconds, but can vary widely. Outputs at 20 Hz will update with a period of 50,000 us (0.05 s), so even if your system jitter is high and around 50 us, this would only affect your timing by 0.1%. Please keep in mind that these amounts of jitter are estimates, and may not be accurate for your system.
If your application must be extremely tightly controlled, and you are seeing higher levels of jitter than your system can tolerate, there are steps you can take to reduce jitter. The best way is to use LabVIEW Real-Time, but this option would most likely involve quite a bit of overhaul to implement. I would recommend simply using a hardware timed output operation in LabVIEW for Windows. Because jitter occurs in the OS, you can write your data to the hardware buffer of your NI-9265, where the sample clock will not have any interference from Windows. To see the difference in a hardware and a software timed operation, launch the NI Example Finder by navigating in LabVIEW to Help»Find Examples. Next, select Hardware Input and Output»DAQmx»Analog Generation»Current. You will see two examples, Gen Mult Current Updates-Int Clock VI and Gen Mult Current Updates-SW Timed VI. The main difference between these two VIs is the use of the DAQmx Timing VI for setting timing to be hardware controlled. More information on setting up hardware timed operations is available here: http://www.ni.com/white-paper/2835/en#toc5
I hope you find this information useful. If you are concerned with jitter in your system and need an easy way to measure and control it, you could also look into using the NI LabVIEW Jitter Analysis Toolkit. Good luck working with your application.
Regards
Patrick
CLA
