waveform chart data comes from both sides...?!

[TDL85]

Hi,

I'm experiencing something strange with my chart that I can't quite get to the bottom of... I'm acquiring waveform data from 2 separate cDAQs. The data is concatenated into 1 array of waveforms and then displayed on a chart.

The strange thing is, the data from 1 cDAQ starts at the left side of the chart, and the data from the other cDAQ starts at the right.... and they cross in the middle.. never really reaching the end of the chart....

I've attached a screenshot of the chart.

Has anyone ever experienced anything like this? I couldn't seem to find much info on why this would happen... I'm quite baffled. Any help would be appreciated.

Thanks!

[altenbach]

Can you place an indicator on the array of waveforms, run the VI for a while so the indicator contains typical data, then convert the indicator to a constant, place it on the diagram of a new VI, and attach it here?

Where do the timestamps for the waveform data come from?

[crossrulz]

Some code would be nice to have.  Here are the couple things I would check:

1. Cheart properties.  People like to change these for some reason and make things not work nearly the way they should

2. Look at the T0 of the waveforms.  Are they different?  This is likely your cause.  Again, need code in order to try to find an issue here.

[JÞB]

I'd look for something like this in the code somewhere

[altenbach]

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@crossrulz wrote:

Some code would be nice to have.  Here are the couple things I would check:

---

The chart properties (specificall the "update mode") is global to all plots and it unlikely to be the problem here.

Is it really a chart or could it be a graph with multiple x-axes, some inverted? (charts can only have one x-axis so you cannot have one regular and one flipped on the same chart (as Jeff suggested))

Yes I suspect t0 and dt of the waveforms. Maybe some have a negative dt?

[TDL85]

Hi,

Thanks for the responses all! It is definitely a chart, and not a graph. I really haven't done any t0 manipulation... I've attached a screenshot of where I'm generating the data. From here it goes into a notifier that feeds the chart on the front panel of the main vi.

In the corner is a constant representing typical waveform data.

I'm using the Continuous Measurement and Logging (NI-DAQmx) sample project as the backbone of all my code, if that helps with the bigger picture...

Thanks again!

[TDL85]

I've also confirmed all of the t0 timestamps for all the waveforms are the same.

[crossrulz]

Then I'm left with some settings in your chart.  Can you post an actual VI with your chart?

[TDL85]

Whoa, I actually had a flawed method of checking all the timestamps... the t0's are not the same! The t0 data from one cDAQ differs from the other cDAQ by ~15 mins....

Even though I'm starting both tasks at the same time.... That is very strange... I can coerce all the t0's to really be the same, and that seems to work... but I feel like I shouldn't have to do that....

I hope this isn't a band-aid that's concealing a larger problem...

[LaurePower]

So after correctring your flawed method of checking data are you getting the uysability you expect? Forcing the t0's to be the same should indeed fix the problem.