DAQ filter data refresh

[alex.]

I am following the example of niScope EX Digital Filtering.vi

It works all right. Every time will refresh almost the same kind waveform.

After I integrate it into my program, the first display of data and the following display data is different. Evertime like this.

May you give any suggestion?

[alex.]

more attachment vi

[Paul_C.]

Hi Yu Ming,

I have tried opening the vi's that you have attached and they seem to be missing a few additional VI's and variable definitions.  Are you able to reproduce the same noise with the niScope EX Digital Filtering.vi example (Help » Find Examples » Hardware Input and Output » Modular Instruments » NI-Scope » Measurements)?  Also, could you provide which digitizer and version of NI-Scope you are using?  Are you able to sample a clean signal with another digitizer or scope?  In addition, what is the rate of the signal and what type of filtering are you applying? 

With a little more information about your equipment and application, I might be able to better assist you in determining the source of the problem.  If you can reproduce the same effect with the shipping example described above, please let me know the exact settings you are using and the characteristics of the signal you are sampling. 

Thanks,
Paul C.

[alex.]

I think it is not a noise, just when switch trigger source from hardware to software, the hardware connection seems has high priority even the software connection is still on.

I have attached vis in the attachement.

[ryan_d]

Hi Yu Ming,

I’ve looked through your VIs and am having trouble determining what exactly might be causing this problem. From what I can tell from you code, the first iteration is being fetched and filtered just like the example, but you want to do additional filtering with the Filter_1channel.vi. I think that you’re not initializing this VI correctly or the VI does not correctly handle the first iteration. Please post back with a description of what exactly you are trying to accomplish with the Filter_1channel.vi and any algorithm, formula, or code that you’re basing this VI on (if any) so I can better see what you’ve started with and what you’re trying to do.

If you have been able to reproduce this problem with any scaled down code, please also post that.

[alex.]

The Filter_1channel.vi is a peak detection program, it will seperate the time axis into small windows and detect the peak value inside these small windows, finally only show these peak values

Total length 400000

Each window 400 points

After filter each cycle 1000 points

400000=400x1000

[alex.]

but actually I have 2 waveform plot, the one with error is not using the Filter_1channel.vi, it will be show directly.

[ryan_d]

I have modified the VIs you've posted from above and simplified them to something that I can run in order to try and reproduce the error you are seeing. Unfortunately, this did not happen.  Although we don't normally modify customer code, I felt like this could help us reach a solution faster. I would like to ask that you eliminate all extraneous code from your VIs and post a scaled down version that still produces the error. I would also like you to post steps to reproduce the error, including information on how to reproduce your source signal. This is important because it allows me to work with your exact configuration, which will help me find a solution sooner along with having material which reproduces the error to show R&D if need be.

[ryan_d]

Message Edited by ryan_d on 10-12-2007 01:20 PM

[alex.]

ok, solved.