Re : Re: Re : Re: waveform chart refresh

[samerham1]

Hello,

i have a little problem with waveform chart,

everytime the shared variable array value changes, the charts already on the waveform are erased, then all charts appeared from the right one second later.

For example: I got 2 charts on the wafeform; when i add a third chart then the 2 old charts are erased then one second later i got the 3 charts.

I just want the waveform to add the third chart without erasing the old charts. I need to have a continuity... How can i do that ?

[Ben]

When adding the new plot first grab the history in the chart. Add another waveform (for the new data) that has empty Waveforms. Pass this to the History of teh WF Chart and THEN start presenting your new data.

Ben

[samerham1]

Add another waveform (for the new data) that has empty Waveforms

I didn't understand what you mean...could you show me the picture or the VI ?
Thx,

[samerham1]

Hi,
you are suggesting to connect 2 inputs to the history of the WF; the first input is when i grap and the second one is the empty weveforms...
please how can i do that ? could you help me ?

[Ben]

Please post-up some simple code demoing what you have so far and we'll advise.

Trying to help,

Ben

[samerham1]

Hi, Thx for reply

In my VI i want to display shared variables from an OPC server. I have tne variable names and their URL as inputs. When i choose a variable it is displayed using  Real-Time Trend.
The problem is when i choose another variable the display of the old variable disappeared for 1s then the Waveform Chart display starts over with the 2 variables.

Please find enclosed 2 files: "NI_event_live.vi" and "NI_event_live_test.vi"

In NI_event_live.vi i have the problem of the refresh of the waveform Chart

In "NI_event_live_test.vi " I tried to dolve the problem but in vain...In fact i tried like you told me to recover historical data when i double-click on a variable then i make a comparison of time in order to maintain the old historical data but i didn't succeed.

Could you help me ?

[Ben]

This a variation on your working demo.

I'll leave deleting an arbitrary plot as an exercise for the reader.

Ben

Message Edited by Ben on 07-03-2008 09:55 AM

[JeffOverton]

Since you want a history ("continuity") in your display, have you considered charts?  The reason your graph is blinking out and back in is that a graph will display all the data written to it, every time data is written to it.  So when you change a shared variable, the graph sees new data, blanks whatever was originally on it, and writes all the new data to the screen.  A chart appends this data.

[samerham1]

Hi,

but i am using a waveform chart to display my variables; is there a difference between " chart" and "waveform chart" ?

[samerham1]

Hi,

i made the changes as you told me.

I made the same changes on "delete a trace" but even so it is not working ! (the first variable disappears)...please find encolsed the VI.
could you tell me why ?