How Can The Time Axis Scroll More Smoothly?

[joerg]

When displaying a faster moving signal, like something that has signal content up to about 30Hz bandwidth, it is best to only show a few seconds in the graph window. No problem. But now the graph jumps at half second intervals. This causes a lot of fatigue when looking at it, it is very uncomfortable. How can the horizontal scrolling be made smooth like it is on a real strip chart recorder or on an FFT waterfall display, without any jagged horizontal movement?

Regards,

Joerg

[AzeoTech]

The refresh rate of a graph is determined by the page refresh rate. You can change this by right clicking on the page name in the workspace and selecting "Properties", then changing the refresh rate. The default is 0.5 seconds. Anything smaller than 0.03 is a waste of CPU power since that yields 30 fps, which is about the limit of what the eye can see.

This is not your case, but I'll say it anyway: If you are doing slow data, say every 5 seconds and want the graph to scroll smooth, you need to feed the graph some faster data. The easiest way to do this is to add another trace to the graph:

Y Expression: 1

X Expression: systime()

Then the graph will scroll with the refresh rate of the page because systime() will always be the time of refresh and that will cause the x axis to scroll. You can make the Y Expression any scalar value.

[joerg]

Thank you. I saw your response in the Labjack forum and responded there. systime() got it working but still not quite as smooth as the roll mode display from my scope of analyzers when piped over to the PC. With DAQFactory the max refresh rate I seem to be able to obtain is 10Hz. On the other stuff it's pretty much realtime at the full 60Hz, making for a smooth rolling. Much of that software is custom, as shipped with the equipment. Some are .NET based routines.

[AzeoTech]

Custom software will always perform better. A custom tool can optimize for a particular situation, and take advantage of technologies (like DirectX) designed for animation, that are difficult or impossible to implement in a flexible tool like DAQFactory. We don't know your application so have to design for a sort of least common denominator. One big thing we do is to draw graphs in the idle thread priority of Windows. This makes it so complex graphs don't bog down the user interface, but also gives a lower max animation rate, possibly slower than the page refresh speed.