Graph data at a certain sampling rate

[abdel2]

I am acquiring data at a sampling rate of 50kHz and I want to plot it on a graph or a chart continuously. The data is in an array which is connected to the graph/chart. I can see the signal (sine wave) but the time scales are not right. I have set "multiplier" field to 0.00002 to reflect my sampling rate but the start and end of the graph are not correct. They usually have a width of about 25 ms. How can I change it to 30 seconds? The graph should always be showing 30 seconds of data at any given moment. 

[RavensFan]

Do you want it to be a graph or a chart?  They are 2 fundamentally different things.  A chart maintains a history of previous points and you can add to it a point or several points at a time.  A graph has no history and it only shows what you send to it at a given point of time.

One problem you'll have with a 50kHz sample rate and 30 seconds worth of data is that is 1.5 million samples.  That is way too many to truly be able to see on a graph or chart at one time where even a large display might only be 1000 pixels wide.

If you are using a waveform chart, you are probably seeing a limit on the chart history length which by default is 1024 data points.  At a 50kHz data rate, that would be about 20 ms worth of data.  Set the chart properties to have a larger history length.

Message Edited by Ravens Fan on 10-03-2008 11:52 AM

[abdel2]

Thanks!

I don't care if it's a graph or a chart. Viewing the history of the data is not a requirement. Besides when we are recording hours of data, it will take up a lot of memory.

I just increased the channel history size and now I can view data for 30 seconds (chart option). It doesn't look that good so I changed it to 5 seconds which is better. It also creates a scroll bar to view some recent data which is pretty nice.

Now I just need to clear the graphs at the beginning and make sure the time interval (5 seconds) is reset when I zoom in and out of the graph. Shouldn't be a big problem, hopefully.

Thanks again.