How do I adjust the min and max values for the x axis on a chart?

[kyle99]

I am trying to adjust the min and max values on the x axis of a chart that is used to display waveforms from a daq card. I right click the chart, select x scale and then formatting. This displays the chart properties dialog box. Selecting the scales tab allows you to adjust these values but it prevents me from selecting a max value that is more than 100 greater than the minimum value. Also, in the help window for the chart properties it says to select .001 for the multiplier under the "Scaling Factors" if you want the scale to display in milliseconds. I currently have the multiplier set to .25 and it correctly displays the data in milliseconds. Can anyone explain the discrepancy? I have attached the vi in version 8.5.

Thanks

[RavensFan]

You can't set the x-axis range to be greater than 100 because your chart history length is only 400.  That means you can only show 400 points, and with a 0.25 dt, that means you can only show a range of 100.  Increase your chart history and you will be able to increase your range.

The reason that a .25 multiplier works is that you are acquiring at a rate of 4 kHz.  So a .25 multiplier means you hare at 1000/second or 1 millisecond.

By default on a waveform chart, the number does not truly mean time, just number of samples.  The x-axis only takes on a meaning of time when you relate the sample number to a time segment by way of the dt property.

Message Edited by Ravens Fan on 02-09-2009 11:45 PM

[JeffL]

Hi kyle99,

Ravens Fan is completely correct. There is no 'time' factor to the chart. The 0.001 factor would be used if you wanted to show seconds as whole numbers. If you want each point to be a millisecond, then you're doing it right with the 0.25 based on your sampling rate.