Different positions of time steps on Time scale for multiple plots of same signals

[Mnuet]

Hi,

   I am facing a strange behavior of graphs of time-domain signals in "Data View". I am using DSA devices to acquire signals. I am plotting three analog voltage inputs (attached to Ch0, Ch1 and Ch2 of same DSA device). The vertical scales of these three signals should be same and follow the maximum signal level. So I plot these three signals on one "Display" in "Data View" and duplicate three such displays. For first "Display1" I change interpolation such that only first signal (Ch0) is visible. On the second "Display 2" I change interpolation such that only 2nd signal(Ch1) is visible. Similarly third signal(Ch2) is displayed on third "Display 3". Now for these three displays, the time scale is not the same. The starting point is 0 and is aligned among these three displays. The end points of time axes are different. For example these are 989.966m, 990.391m and 1.00034 for 102400 points acquired at sampling rate of 102400  Samples / second. Similarly the major grid lines are also not aligned among these three graphs when we move towards end of time scale.

    I have tried changing "Time Stamp Type" to "Relative to Ch0" for all three displays but this problem remains same. I tried my best to work around it but could not succeed. I tried to save the signals and then plot after reloading while taking same time information from column 1. This solved the problem of time axes but now auto-scale stops working on vertical scales whenever signal amplitudes goes down (The scale does not follow decreasing amplitude of signal but remains fixed).

   Can anyone help me in this matter? I shall be very thankful for an earlier response.

[Vivek_N]

Hi,

I wanted to clarify what exactly you are trying to accomplish. Do you want the end points on all the time axes to be the same? Is this to just align the time values in all the displays? If so, do you need these time values aligned for the saved data or in the display view as well? Any details on what you are trying to do would be appreciated.

[Mnuet]

Hi Vivek

   I need to align time values in all the displays (in Data view). The time values should already be aligned since I am using DSA PCI-4474 which is a simultaneous sampling digitizer.

    I explored it in detail. If I add displays in Data Views while there is no data acquired and save the project then it works fine. However if I save the project after acquiring data and doing some zoon In/ zoom out etc. then I face this problem. Please let me know if there is a way to avoid it.

Moreover I need a confirmation from you on my following application development:

I have a simple application of showing 12 analog signals on 12 different graphs placed vertically in aligned position. I have to develop a user interface so that if user wants to display signal no. 1, 4 and 6 out of total 12 signals, he should make selection using check boxes and click a re-draw button. It should result in these three signals displayed as separate graphs aligned vertically and adjusted to fit window size of Data View. Similarly later user can change his selection of displaying signals (from same acquired data) say 1, 3, 5, 6, 8, 9, 11 & 12 and click Redraw button. It should result in clearing of Data view (or opening a new Data View tab i.e Data View 1) showing all these signals as separate graphs which are aligned vertically and resized to fit the window.

Can I achieve this user interface design using Signal Express only (without using Lab view)?

Regards
Mnuet

[Vivek_N]

Hello Mnuet,

I tested this out on my side with one DAQ card. It does not look like SignalExpress has any settings available to align all the displays by time scale. I would recommend filing a Product Suggestion for this. You can do so at http://digital.ni.com/applications/psc.nsf/default?OpenForm . I will do this on my side as well. I will definitey let you know if I do find any workarounds for this.