How do I format x-axis to show time in seconds on a waveform chart?

[msmartei]

I am trying to format the x-axis so that it shows time in seconds, as opposed to the current format in which it is. I have tried tweaking the format option to display as <%S> but it still is not correct.

Any suggestions?

The VI and a sample graph with the current 'second' scale is attached.

Thanks!

[Hillman · Accepted solution]

Hi msmartei,

Firstly, have you seen this knowledgebase article?

Displaying Current Time on a LabVIEW Chart

http://digital.ni.com/public.nsf/allkb/6F0054EEABAFE4B886256F2700012142?OpenDocument

These properties allow you to display time fine, it works for your chart.

 You can then use property nodes to alter the start value, displayed range and maximumn values for example. You can also edit the color, style of the plotted lines for example.

Hope this helps, 

Message Edited by Hillman on 06-02-2009 11:56 AM

Message Edited by Hillman on 06-02-2009 11:59 AM

Message Edited by Hillman on 06-02-2009 12:04 PM

[msmartei]

Hi Hillman,

Thanks for the reply and the knowledgebased article.

I tried it and it seems to work fine. Is there anyway of ensuring that the update occurs in realtime seconds, i think that the current rate (i have the multiplier set to 0.001) is a bit on the fast side. Do i just have to tweak the update rate?

Thanks,

Margaret

[Dennis_Knutson]

Your output labeled Actual Input Rate should be used with the Reciprocal functions. Then, if you change the sample rate, you don't have to change anything else.

[msmartei]

Jinx! I just finished putting in the reciprocal function when i saw this message.

It didnt make any difference since i was already using the calculated inverse as the input into the multiplier.

Semi-relatedly, is there anyway to save the plots for each cycle of the while loop? So that as opposed to it getting replaced after every run, i can still refer to the "old" results.

Thanks!

[Dennis_Knutson]

How many plots do you want to save. Right now, you have the chart history set to the default of 1024. The front panel number of samples is set to 500 so you will display slightly more than 2 iterations at a time. You can increase the history size to show more.

[Hillman]

Hi Margaret,

Thanks for the reply, and can see Dennis has been helping you out some more.. do you have any more issues with the chart?

 When you say update do you mean that the waveform disspears quickly from view? If so, just increase the range property to a couple periods of the waveform your expecting. Or do you mean, the actually chart doesn't display new data quicker enough/two quickly? I think you meant the first, but just want to check. 

Please let me know.  

[msmartei]

Hillman and Dennis,

Thanks for all the help.

I changed the while loop to a for loop that executes once because that is all i need to capture the change in the voltage at the piezos. So far so good, the piezo works the way i want it to. I will let you know if i run into any more problems.

Thanks once again!

msmartei