waveform relative time

[AzimJ]

In Labview 8.5 I want the x-axis to show the elapsed time of data collection relative to when the data collection was started.  When I set the time property to relative it shows some huge number of seconds (see attached jpg)?

thanks

Azim

[mikeporter]

The huge number of seconds is probibly the current time from when you did the screen capture. The number of the left relates to 7:41:57 pm, 23 Dec, 2008. (East Coast US Time)

Mike...

[AzimJ]

I did change the X-scale to relative time as suggested in another post. So it is not relative time then (since 7:41:57 pm, 23 Dec, 2008 East Coast Time) is the absolute time of when I collected and displayed the data. So, I would like to know how to make the number on the left zero and the number on the right the elapsed time.  Is it a matter of subtracting the absolute time from the data.  The data going into the graph is a 1-dimensional array of waveforms.  So do I have to:

1. split this array into it's individual componenets 
2. extract the Y-data for each signal
3. rebuild an array  or cluster containing all 4 waveforms
4. somehow tell the graph the sampling frequency of the signal and 
5. wire up the newly created array to the graph.

Or is there some other way for the X-axis to display the range (0-8) since this is displaying an 8 second waveform signal?

Thanks for all the help

[kikiduu]

ZimR,

The problem is you are using waveform chart to display a wavefrm which has non zero t0 value (in this case the start time 7:34 23rd december). So either you make t0 as zero and display in waveform chart or use a waveform graph with 'Ignore timestamp' property selected.

Message Edited by kikiduu on 12-24-2008 12:26 PM

[Robbob · Accepted solution]

As kiki mentioned,

Use 'Build Waveform.vi' and set the property 't0' to zero.  If you have an array of waveforms, pass this into an auto-indexing for loop so you can do it to every waveform in the array.

[Ljubo]

Hi, ZimR !

As I understand I have a similar problem sometimes. You can see my solution in attachements.

To simulate data acqusition I used the same value for  Number of Samples and Time Delay in while loop. Don't forget to set "Chart History Length ..." value to something bigger, 20000 for example. The default is 1024.I don't know how to change this value in run time mode (if it is possible). This is the question for someone else.

I hope it helps.

With best regards,

Ljubo.

[AzimJ]

Thanks for all the answers.  I tried to tell the waveform chart to ignore the time-stamp but that didn't seem to do anything. So,I see that the solution is to set the time-stamps of the waveform to zero. 

Azim