Periodic writing to graph

[RL]

I want to plot a new point to a 1200 pixel wide graph every 500 ms.  The graph should be fixed in place and always be visible as the line progresses from left to right.  A cursor is required so charts are out.  Some of the examples that write to the Shift Register are scrolling the Graph therefore the line is always moving.  I want to fill the graph from left to right but nothing moves except that a point is added every 500 ms.  This is not obvious to me, I need expert advice.

using Labview 7.1

Raymond

[DavidJCrawford]

There is an example called Variable-Time Chart XY shipped with LabVIEW.

Maybe there are elements of that example you could use to get you started.

David

[RL]

David,

Thank you for the information but Examples Search in LV 7.1 does not show Variable-Time Chart XY.  Is it possible that it has a different name?

Raymond

[DavidJCrawford]

Its definitely there on LV 7.1 FDS

David

Message Edited by David Crawford on 10-23-2006 03:21 PM

[RL]

David,

Thank you. The XY Search brings it up but Variable-Timed did not. 

I am looking for a graph in which the X axis shows the elapsed time and the plot line starts at 0 and moves towards the right over a period of say 10 minutes (about 1 pixel every half second).  It should not scroll or be deformed to fill the screen just a simple progression to the right.  I would have though that this is the most basic of graphs but I can't find an example. It looks like everything insists on filling the buffer for a full capture then it is displayed.

Raymond

[DavidJCrawford]

Hi Raymond

Take a look at this vi. Its uses an XY-Graph where the X-axis autoscale is off, loose fit is off and the x-axis format is relative time in HH:MM:SS. I setup the X-Axis maximum to be 600 seconds.

This VI will run for 1200 samples at 0.5 interval which is the 10 minute duration.

Hopefully this will get you started.

David

[RL]

David,

I was trying that a while ago and tried the parameters on the  VI you just sent but it writes the accumulated points rather than plot one point per 500 ms.

I need a graph that does a screen refresh every  500 ms to bring out the latest point.

Unfortunately I let my support lapse and I am having a lot of trouble getting this basic graph to work.

Raymond

[DavidJCrawford]

Raymond

I am sorry, but I am having trouble understanding what you want.

David

[Dennis_Knutson]

You should post what you've written. A graph will be updated with whatever data you send it and if it updates with accumulated data, then that is what you are sending instead of just the last single point. It's usually pretty obvious as to the type of data that is wired to the graph. Is it an array or scalar?

[RL]

David,

Thank you for your patience.  I am having difficulty describing this since I don't have the correct words.

The graph should appear with an X axis starting at 00:00 (that is 0 minutes & 0 seconds) and ending at 10:30 (10 minutes & 30 seconds).
The first point is written at 00:01 (either the plot line starts there or it links the 00:01 data point to the origin).
The second data point is written at 00:02 - with the connecting line reaching from 00:01
The third data point is written at 00:03 - with the connecting line reaching from 00:02

There is no graph movement except for the data points being added incrementally from left to right.  Once they are plotted they do not move nor does the X axis more.

The acquisition stops when the 10:30 data point is written (which means that the graph line has reached the right side of the graph).

Is this better?

Raymond