Jittering on the FlexLogger High Speed Graph Display

Issue Details

I am trying to use high speed signals in FlexLogger, but the graph display appears to jitter or stutter. Data points render unevenly, and the graph trace may jump or lag rather than scrolling smoothly. This behavior is most noticeable at higher sample rates or when multiple channels are displayed simultaneously. Why is this happening?

Environment: FlexLogger 2024 or later and Windows 

Solution

The root cause is related to how Windows allocates CPU time to applications. FlexLogger runs as a standard priority process by default. When other applications or background services compete for CPU resources, Windows may temporarily deprioritize FlexLogger's rendering thread, causing visible jitter in the graph display. Because Windows is not a deterministic operating system, it does not guarantee consistent timing for UI rendering regardless of system load.

The solution is to make FlexLogger have a higher priority in Windows, by setting it's priority to a higher level.

1. Open Task Manager by pressing Ctrl + Shift + Esc, or right click the Windows icon on your Windows Dashboard and selecting Task Manager
2. Click the Details tab in Task Manager.
   
3. Locate the FlexLogger process in the list. It will appear as FlexLogger.exe. If multiple FlexLogger related processes are listed, identify the main application process (typically the one with the highest memory usage).
4. Right click FlexLogger.exe and select Set priority.
5. Select High or Above Normal from the priority options. Do not select Realtime, as this can cause system instability by starving critical Windows services of CPU time.
6. A confirmation dialog will appear. Click Change priority to apply the setting.

Additional Information

• Raising the process priority improves the consistency of the graph rendering but does not guarantee a perfectly smooth display. Windows is a general purpose operating system and does not provide deterministic thread scheduling.
• Hardware interrupts, driver activity, and other kernel level operations can still cause occasional rendering delays regardless of the application's priority setting.
• The logged data itself is not affected by this issue, as DAQmx handles acquisition independently of the FlexLogger UI rendering thread. The jitter is a display artifact only and does not indicate data loss.